Loudspeaker line array configurations and related sound processing

ABSTRACT

A sound reproduction system includes one or more arrays of drive units, coupled with sound processing allowing improved steerability, directional control, width control, and/or beam overlay. A speaker column may comprise two arrays facing one another, the drive units being perpendicular to the speaker unit front, with the acoustic output of each line array being compressed, turned and output from an elongate slot. The drive units may be staggered with respect to those in the opposing array. The arrays may be arc-shaped else straight. Selective delays to simulate an arced pattern. Differential delays applied to the drive units in a sub-array allow beam steering. Additional drive units, such as high frequency drivers, may be added along the length of the elongate slot or elsewhere to increase the dynamic frequency range of the speaker system. A collocated sound processor and amplifier output stage may be integrated with the speaker unit.

RELATED APPLICATION INFORMATION

This application claims the benefit of U.S. Provisional Application Ser.No. 60/829,640, filed on Oct. 16, 2006, hereby incorporated by referenceas if set forth fully herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the present invention relates to sound reproduction and,more specifically, to loudspeaker array configurations and related soundprocessing and systems.

2. Background

Sound reproduction systems incorporating speakers are commonplace inhomes, theaters, automobiles, places of entertainment, and elsewhere.The number, size, quality, characteristics, and arrangement of speakersaffect sound quality in virtually any listening environment. However,many environments have constraints which limit the number, size, or typeof speakers which can be used, and their arrangement. These constraintsmay be technical, mechanical, or aesthetic in nature.

The listening experience involves not only the speaker but also itsinteraction with the listening room or area. The total sound arriving atthe listener has two components—direct and reflected. The direct soundprovides clues as to the perceived direction of the original sources,while the indirect component increases the apparent loudness, sense ofspaciousness, and general ambience. These indirect effects are mostlypositive in the sense that they tend to enhance the listeningexperience. But reflections can also color the sound, leading tounnatural changes in timbre.

Besides the potentially undesirable effects of indirect or reflectedsound, the acoustic character of the listening room or area can besufficiently obtrusive so as to mask the natural sound quality of theoriginal source material. For example, at low frequencies, standingwaves in a listening area may cause some low frequencies to beemphasized more than others, especially in domestic-sized living rooms.The resulting bass sound is often boomy and very position dependant.

Careful placement of the speakers can reduce some of the aforementionedproblems, but typically provides a satisfying listening experience onlywithin a limited area or “sweet spot.” Such a limited solution may havebeen acceptable in the past, when the audience for critical listeningwas limited to only one or two at a time. But this is seldom true today,when the sound source is usually multi-channel, more often than notaccompanied by a picture, and with many more listeners seated informallyover a much wider area.

With traditional stereo playback, the illusion of a continuous soundstage can be created between the two speakers when the listener isseated symmetrically in front of them. However, in practice, only thoseoriginal sources positioned exactly in line with the speakers can beprecisely located, while those between the speakers, often known as“phantom sources,” depend on the listener being equidistant from both.Any movement of the listener away from a position of symmetry willgenerally cause the phantom image to flop to the nearest speaker, thusdestroying the stereo illusion.

The introduction of a center channel speaker, originally for filmsoundtracks, was intended to eliminate this effect and keep the dialogat stage centre. This it does, but often at the expense of narrowing thefront soundstage. For this reason many critical listeners ofmulti-channel audio source material often prefer to omit the centerspeaker, even if it means a more restricted sweet spot.

Besides the potential problems caused by the shape or characteristics ofthe listening environment, additional difficulties may be presented bythe nature of the speakers being used to reproduce the sound. Evenwell-designed speakers, having a smooth level axial frequency response,can often have an unnatural timbre or colored sound due to reflectionsfrom nearby surfaces. For this reason, the off-axis response as well asthe direct sound from the speaker is desired to be both be smooth andwell controlled. However, the problem of achieving well-controlleddirectivity in loudspeakers has proved difficult to solve. Speakers withsome measure of directional control, such as horn-loaded speakers, haveroutinely been used in the cinema, although their continued use owes asmuch to their higher efficiency as it does to their ability to have acontrolled directional response.

One downside to using horn speakers is that they distort at high levelsdue to the non-linearity of the air at the mouth of the horn.Additionally, their inability to maintain constant directivity over awide frequency range typically requires the use of multiple hornspeakers, each covering a different part of the audio spectrum.Low-frequency horns are extremely large and as a consequence are rarelyused. For reproduction of the low frequencies it is common to employmore conventional direct radiator speaker systems.

Another well known type of speaker system with some measure ofcontrolled directivity, also used for sound reinforcement purposes, isthe so-called column speaker. A column speaker consists of a long lineof closely spaced identical speaker drive units that can provide adegree of directionality in the vertical plane when placed upright.Longer lines permit greater directional control at lower frequencies,with the limit of directional control being generally set byrelationship between the line length and the wavelength of sound at thelowest frequency of interest. The longer the line, the lower thefrequency of beam control can be. The spacing between the driversgenerally limits the upper frequency for control. A two-dimensionalarray, with both rows and columns of speaker drive units, is capable ofproviding control in all directions. The design of such systems isdifficult, and its implementation is very expensive in general.Moreover, not until relatively recently has the processing power neededto provide good directional control over a wide frequency range beenviable. The design of suitable transducers for inclusion in such anarray is another matter altogether. Meeting the dual driver-designrequirements of close spacing, for accurate high-frequency control, andthe need for a large effective radiating area for good bass output arenot inconsiderable. Existing speaker systems which purport to achievesome form of directional control use miniature drivers that are neithersmall enough for high-frequency control nor large enough for adequatebass output.

Coupled with the aforementioned challenges is the fact that, in manyenvironments, it is desirable to minimize the visual impact ofloudspeakers. One technique, for example, is to color or otherwisedecorate the protective speaker faceplate to match the surrounding wallor object in which the drive unit in placed, or to hide the speakersbehind an artificial painting. These types of solutions may not besatisfactory for all consumers, and may limit the possibilities foroptimal speaker placement as well.

One technique that has been proposed for a type of speaker column havingcertain desirable characteristics relates so a so-called ConstantBeamwidth Transducer (CBT) array. FIG. 1 is a diagram showing an obliqueview of an example of a curved speaker line array 100, also known as aConstant Beamwidth Transducer (CBT) array, as known in the art. Asillustrated in FIG. 1, the curved speaker line array 100, or CBT array,comprises a plurality of low frequency drive units 104 adjacent to aplurality of high frequency drive units 108. According to a particulartechnique, the CBT array 100 employs frequency-independent Legendreshading. This technique is described in more detail in, for example, D.B. Keele, Jr., “Practical Implementation of Constant BeamwidthTransducer (CBT) Loudspeaker Circular-Arc Line Arrays,” 115^(th)Convention of the Audio Engineering Society, Paper 5863, October 2003,hereby incorporated by reference as if set forth fully herein. Asexplained therein, a CBT array is constructed using Legendre functionshading of the transducer drive levels in order to maintain what hasbeen described as frequency-invariant pattern control. Each transducerin the array is driven with a different signal level that follows thecontinuous Legendre shading function, with the drive levels graduallytapering from maximum at the center of the array to near-zero at theouter edges of the array (depending upon truncation of the arc formed bythe curved speaker line array 100). The result is a speaker system thatmay provide wideband, extremely constant beamwidth and directivitybehavior with virtually no side lobes.

A similar concept can be extended to a straight-line or flat-panel CBTarrays, with the use of appropriate signal delays. Such a technique isdescribed, for example, in “Implementation of Straight-Line andFlat-Panel Constant Beamwidth Transducer (CBT) Loudspeaker Arrays UsingSignal Delays,” 113^(th) Convention of the Audio Engineering Society,Preprint 5653, October 2002, and “Full-Sphere Sound Field of ConstantBeamwidth Transducer (CBT) Loudspeaker Line Arrays,” J. Audio Eng. Soc.,vol. 51, no. 7/8, July/August 2003, both by D. B. Keele, Jr., and bothof which are hereby incorporated by reference as if set forth fullyherein.

Although CBT arrays have the potential for improved sound reproductioncharacteristics, they nonetheless still suffer from many of the sameproblems as conventional column array speakers. For example, the spacingbetween the driver units sets a limit to the upper frequency fordirectional control.

Another type of known speaker array comprises a two-dimensional array offorward-facing drive units. The two-dimensional array is composed ofindividual line arrays of drive units, with each line array offset orstaggered from the neighboring line arrays. An example of such an array,which has been commercially marketed only recently (and therefore noadmission concerning its potential status as prior art is intended byits inclusion in this background discussion of related art), is theYPS-1 “digital sound projector” available from Yamaha ElectronicsCorporation. The YPS-1 is described, for example, in a product brochureat http://www.yamaha.co.jp/english/product/av/pdfs/catalog/ysp1.pdf, ashaving 40 drive units of 4 cm size arranged in several rows, flanked ateither end by a larger 11 cm drive unit. An on-board digital soundprocessor is apparently provided for controlling the drive units. TheYPS-1 has various connectors including a coaxial video output to link itto a television, several digital inputs (optical and coaxial), and anRS-232C connector.

A two-dimensional array of forward-facing drive units, such as the YPS-1or similar audio units, may potentially suffer from drawbacks such aslobing, and may also have limitations on the upper frequency response.Also, such a two-dimensional array may lack midrange warmth and body,and/or fail to convincingly reproduce certain audio sources,particularly music.

Accordingly, it would be advantageous to provide a speaker system whichhas a less adverse interaction between the loudspeaker and the listeningroom or area, and offers flexible directional control and/orsteerability. It would further be advantageous to provide a speakersystem that has more accurate sound timbre, and/or more accurate,believable and stable sound images over a wider listening area. It wouldalso be advantageous to provide a speaker system that can beaesthetically packaged, and/or provides other benefits and advantages.

SUMMARY OF THE INVENTION

Certain embodiments disclosed herein are generally directed, in oneaspect, to a sound reproduction system having a plurality of drive unitsarranged in a column or array, coupled with sound processing allowingimproved steerability, directional control, width control, and/or beamoverlay. In one embodiment, for example, a speaker column comprises twoarrays of drive units arranged facing one another, separated by arelatively narrow gap. An elongate slot (comprising either a single slotor series of slots) along the length of the opposing arrays provides apath for sound output from the drive unit arrays. The individual driveunits from each array may be symmetrically opposing one another, or elsemay be staggered with respect to the opposite array. Additional driveunits, such as high frequency drivers or tweeters, may be added alongthe length of the elongate slot or elsewhere to increase the dynamicfrequency range of the speaker system.

In another aspect, the drive units in each array may be physicallyarranged in a curved or arc-shaped pattern, such that the centermostdrive unit protrudes beyond the other drive units, and the locations ofother drive units progressively recede upwards and downwards along theedge of the arc. Alternatively, the drive units may be physicallyarranged in a line array. In other embodiments, the pattern isintermixed; for example, only some of the drive units may be arranged ina partial arc, while the remainder are arranged in a linear manner.

In another aspect, an input signal is processed so as to generatemultiple drive unit signals, allowing adjustment or control of thedirectionality or other characteristics of the sound output from thedrive units. For example, where the drive units are arranged in a linearray, the input signal may be delayed in accordance with the driveunit's relative position with respect to the center axis of the speakerunit, thereby simulating the sound characteristics of a curved speakerarray. Other processing techniques as described herein may allowadjusting the characteristics (e.g., widening or narrowing) the audiooutput (or beam) from a speaker line array, aiming the audio beam inspecific direction, outputting multiple audio beams (which may beoverlaid in whole or part), and/or creating virtual or simulatedspeakers using “real” phantom images by selectively or dynamicallycombining drive units into selected sub-arrays. A speaker line array maybe combined with integrated signal processing and/or individual poweramplifiers for each drive unit or for groups of drive units.

In another aspect, a speaker unit is configured with an amplifier outputstage integrated or collocated with the speaker unit, while the firststage of the amplifier is located remotely. The first stage of theamplifier may be embodied in an audio control unit which also includescommand and power distribution capability. Command and/or power signalsmay be communicated from an audio control unit to one or more speakerunits, such as speaker line arrays, which may be located at differentphysical locations. The command and power signals may control thespeaker unit so as to provide a directional or steerable sound image,with one or more audio beams, and/or to create one or more real phantomspeaker images. The power signals may be generated from a tracking powersupply, and may be generally low voltage in nature, on average, withoccasional transient excursions above the normal supply rail level whenneeded to drive peak sound in the audio program. In one aspect, anintelligent digitally controllable speaker is provided according tocertain embodiments as disclosed herein.

Further embodiments, variations and enhancements are also disclosedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a curved speaker line array as known in the art.

FIGS. 2A and 2B are diagrams of a curved speaker line array having aslot for sound output, in accordance with one embodiment as disclosedherein.

FIGS. 3A and 3B are diagrams showing another embodiment of a speakerline array.

FIGS. 4A and 4B are high-level block diagrams of circuits for providinginput signals to a speaker line array.

FIG. 5 is a diagram of another embodiment of a speaker line array,having staggered drive units.

FIG. 6 is a high-level block diagram of a circuit for providing inputsignals to a speaker line array such as illustrated, for example, inFIG. 5.

FIG. 7 is a diagram of a half-curve groundplane speaker line arrayhaving a slot for sound output.

FIG. 8 is a diagram of an example of a partial-curve speaker line array,in accordance with another embodiment as disclosed herein.

FIG. 9 is a high-level block diagram of a circuit for providing inputsignals to a partial-curve speaker line array such as illustrated, forexample, in FIG. 8.

FIG. 10 is a diagram illustrating an example of a sound system usingmultiple speaker line arrays and power amplification stages splitbetween a remote audio distribution unit and each of the speaker linearrays.

FIGS. 11A and 11B are detailed circuit block diagrams of another exampleof an audio sound system, including a power supply/transmitter portionin FIG. 11A and a speaker/receiver portion in FIG. 11B.

FIG. 12 is a high level diagram of various components of a sound systemin accordance with the example illustrated in FIGS. 11A-11B.

FIGS. 13A and 13B are different cross-sectional views of a speaker linearray as may be used, for example, in connection with the sound systemof FIG. 10, FIGS. 11A-11B, or other sound systems.

FIGS. 14A and 14B are conceptual diagrams illustrating the tailoring ofsound beam width using a speaker line array.

FIGS. 15A through 15D are conceptual diagrams illustrating the steeringof a sound beam using a speaker line array.

FIGS. 16A through 16D are conceptual diagrams illustrating thegeneration and steering of multiple sound beams using a speaker linearray.

FIG. 17 is a conceptual diagram illustrating generation of “real”phantom images using a speaker line array.

FIG. 18 is a diagram illustrating an example of a configuration ofmultiple horizontal speaker line arrays in a home theater sound system.

FIGS. 19A through 19D are diagrams illustrating, from differentviewpoints and cross-sections, a particular embodiment of a speaker linearray having staggered drive units.

FIGS. 20A through 20F are diagrams illustrating, from differentviewpoints and cross-sections, another embodiment of a speaker linearray having staggered drive units.

FIG. 21 is a sideview diagram illustrating an example of speaker unitprofile formed by truncating the curved arc corresponding to a Legendrefunction.

FIG. 22 is a diagram illustrating how delay values may be calculated fordrive units of a flatfaced speaker unit to simulate the profile of aspeaker unit curved according to a Legendre shading function.

FIG. 23 is a diagram comparing certain characteristics of a conventionalline array speaker unit having non-staggered drive units with a slotteddual line array speaker unit having staggered drive units.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Certain embodiments disclosed herein are generally directed, in one ormore aspects, to a sound reproduction system having a plurality of driveunits arranged in a column or array, coupled with sound processingallowing control over direction and width of the sound output, as wellas the possibility of generating separate sound “beams” eachcontrollable in terms of content, direction, and width. Variousconfigurations of speaker line array are particularly advantageous foruse in such a sound reproduction system. For example, a speaker columnmay comprise a single array of low frequency drive units, oralternatively may comprise two arrays of low frequency drive unitsarranged facing one another, separated by a relatively narrow gap. Inthe latter case, the individual drive units from each array may besymmetrically opposing one another, or else may be staggered withrespect to the opposite array. An elongate slot (comprising either asingle slot or series of slots) along the length of the opposing arraysprovides a path for sound output from the drive unit arrays. Additionaldrive units, such as high frequency drivers or tweeters, may be addedalong the length of the elongate slot or elsewhere to increase thedynamic frequency range of the speaker system. The line array may becurved, partially curved, or straight; however, the sound processing maydiffer depending on the physical configuration of the drive units.

Embodiments as disclosed herein may be employed in a variety ofapplications, and may be particularly well suited for situations inwhich it is desired to provide a sound system providing a high degree ofcontrollability over the direction and width of the sound output. One ormore speaker line arrays may be advantageously employed in applicationssuch as cinema, home theater, clubs, recording studios, amphitheaters,and various indoor or outdoor installations. Speaker line arrays mayalso be advantageously utilized in connection with flatscreen televisionmonitors, desktop computer monitors, and so on, for providing improvedaudio controllability with computer or video games or the like.

FIGS. 2A and 2B illustrate a curved speaker line array 200 having a slotfor sound output, in accordance with one embodiment as disclosed herein.FIG. 2A is an oblique view diagram of a speaker unit 200, which, in oneaspect, may be viewed as a type of speaker column. As illustratedtherein, the speaker unit 200 may (but need not) have two side walls233, 234 with a curved front faceplate 237 (which may comprise left andright sides) spanning therebetween. The curvature of the front faceplate237 preferably follows an arc based on a continuous Legendre shadingfunction, or a truncated portion thereof. The speaker unit 200 mayadditionally have a top wallplate 232 and a bottom wallplate 231, eachinterconnecting the side walls 233, 234 and the front faceplate 237.

The speaker unit 200 further comprises two curved speaker line arrays214, 215 each comprising a series of drive units 204, 205 (shown withdotted lines). The drive units 204, 205 are preferably low and/or midfrequency range drive units, although in other embodiments they may havea different frequency range. The drive units 204, 205 of the two curvedspeaker lines arrays 214, 215 in this example are positioned facing oneanother, separated by a relatively narrow and elongate sound output slot225. The elongate sound output slot 225, which may comprise either asingle slot or series of slots, runs along the length of the twoopposing speaker line arrays 214, 215 and provides a path for sound tobe output from the drive units 204, 205. In this particular example, aframmel or dividing wall 226, preferably comprised of a material havinga non-resonant characteristic, runs down the length of the main soundoutput slot 225, dividing it into two parallel sound output slots (leftand right) 225 a, 225 b. The first sound output slot 225 a provides apath for sound to be output from the first speaker line array 214, andthe second sound output slot 225 b provides a path for sound to beoutput from the second speaker line array 215. The drive units 204, 205are preferably mounted on a baffle or other similar structure, in amanner acoustically isolating their forward sound radiation from theirrearward sound radiation.

FIG. 2B illustrates a cutaway side view of the central right portion ofthe speaker unit 200 shown in FIG. 2A. In FIG. 2B, the drive units 205are shown in solid lines, positioned in an arc along the curved frontfaceplate 237 of the speaker unit 200. In a preferred embodiment,acoustic absorbing material (such as, e.g., compressed foam) 239 isplaced within the rear duct of the sound slot 225, circumjacent to theouter rear contours of the drive units 205. The acoustic absorbingmaterial 239 is similarly disposed on the opposite side of the speakerunit 200, with respect to drive units 204. The acoustic absorbingmaterial 239 provides a barrier on the rear side of the drive units 204,205 and, along with the dividing wall 226, forces the sound output fromthe drive units 204, 205 to be generally compressed, turned (at a ninetydegree or other sharp angle), and projected from the sound output slots225 a, 225 b. In one aspect, the sound output slots 225 a, 225 b ineffect transform the size, shape, and/or aspect ratio of the drive units204, 205, having an impact on the stability and directionality of theapparent sound image.

The acoustic absorbing material 239 may help prevent, e.g., undesirableinterference or reflections within the duct or chamber, that mayotherwise be caused by soundwaves reflecting from the backwall or backcorners of the duct, since the soundwaves have no means of egress exceptthe slot 225. The acoustic absorbing material 239 may in certainembodiments also help to prevent the creation of standing waves, and/orminimize the variation of sound output response with respect tofrequency so that the speaker output can be readily equalized by, e.g.,any standard techniques, including analog or digital equalization. Forexample, cascaded filter sections may be employed to tailor thefrequency response of the drive units 204, 205 in discrete frequencybands so as to provide a relatively uniform overall frequency response.

The acoustic absorbing material 239 in FIG. 2B, and other embodiments aswill hereinafter be described, may comprise any suitable material, andis preferably non-resonant in nature, with sound absorbing qualities.The acoustic absorbing material 239 may, for example, comprise expandedor compressed foam, or else may comprise rubber, reinforced paper,fabric or fiber, damped polymer composites, or other materials orcomposites, including combinations of the foregoing materials.

Since an effect of the dividing wall 226, sound output slots 225 a, 225b, and acoustic absorbing material 239 is to compress the sound wavesoutput from the drive units 204, 205 and turn them towards the terminusof the sound output slots 225 a, 225 b, the drive units 204, 205 mayhave to work harder to overcome the resistance inherent in compressingthe sound waves and having them redirected. At the same time the overallspeaker unit 200 may have a narrower output profile and gain benefits interms of directional control and characteristics. Further details of aslotted speaker construction are described, for example, in copendingU.S. application Ser. Nos. 10/339,357 filed Jan. 8, 2003 and 10/937,76filed Sep. 8, 2004, both of which are hereby incorporated by referenceas if set forth fully herein.

In a preferred embodiment, the dimensions of the sound output slots 225a, 225 b may be selected based upon various factors including, amongother things, the expected frequency range of the audio output.Referring to FIG. 2B in particular, the sound ducts terminating inoutput slots 225 a, 225 b may be relatively truncated in nature; thatis, the spacing from the outermost edge of the drive units 204, 205 tothe curved front faceplate 237 may be kept relatively short, to avoid,e.g., the buildup of standing waves or turbulence, and also to minimizethe work needed by the drive units 204, 205 to force the compressedsound waves towards the terminus of the sound output slots 225 a, 225 b.By preventing soundwaves from drive units 204, 205 to unfoldsignificantly within the confines of the sound duct, the soundwavesemanating from the output slots 225 a, 225 b may have sound quality anddynamic range comparable to the soundwaves initially emitted from thedrive units 204, 205 themselves. The width of the sound output slots 225a, 225 b may be selected narrow enough to provide broad directionalcharacteristics over the frequency range for which the wavelength ofsound traveling in air is large compared with the slot dimensions. As anexample, the width of the sound output slots 225 a, 225 b may be in therange of 8 to 12 millimeters. Narrowing the width of the sound outputslots 225 a, 225 b may potentially decrease the efficiency of the driveunits (which may be compensated by larger drive units and/or increaseddrive power), or may cause audible noise from turbulence. Therefore, thenarrowness of the sound output slot 225 a, 225 b may be limited by,among other things, impedance losses that cannot be made up by increaseddrive power and the onset of sound artifacts or noise caused byturbulence or nonlinear airflow.

A potential benefit of a speaker unit arrangement in accordance withFIGS. 2A-2B, and other slotted speaker unit arrangements as describedherein, is that sound emanating from the output slot 225 may generallytend to have a wide dispersion angle along the slot's long axis, ascompared to the dispersion angle of a conventional forward-facing driveunit or line array. Thus, the speaker unit 200 may possess an extremelybroad directional characteristic over the frequency range for which thewavelength of sound in air is large compared with the slot dimensions.Because of the wide dispersion angle along the long axis, the speakerunit 200 may provide a similar listening experience with respect tooff-axis listeners at a variety of locations away from the center axisof the output slot 225. The advantageous dispersion characteristics maypermit design choices that, for example, account for the relativelikelihood that listeners will be positioned along one or the other axisof the soundwaves emanating from the output slot 225. These designchoices, generally not available for equiaxed drivers, are particularlyadvantageous in confined listening spaces.

In one aspect, the sound ducts of speaker unit 200 associated with eachof the drive units 204, 205 and terminating in output slots 225 a, 225 beffectively “turn” the soundwaves output from the drive units 204, 205(by 90° in this example), so that the sound is carried to the outputslot 225 and released while retaining a sufficient degree of soundquality, and modifying the effective shape of the speaker output from anelliptical or circular radiator (as the case may be for drive units 204,205) to an elongated rectangular radiator. In addition, the totalradiating surface area can be advantageously reduced, as compared to theradiating surface area of the drive units themselves, minimizing thespace needed. The aspect ratio of the sound output slots 225 a, 225 bcan be adjusted or tailored to modify the directional characteristic ofthe acoustic output in order to, for example, improve sound quality atoff-axis listening positions.

In the example illustrated, the individual drive units 204, 205 arearranged symmetrically so that they directly oppose one another,although, as explained later herein, in other related embodiments theymay be staggered with respect to the drive units in the opposite linearray. Among other advantages or benefits, in addition to differences instability or directionality of the sound image, the arrangement of FIGS.2A-2B whereby the drive units 204, 205 are at a right angle to thedirection of sound output allows a narrower front sound output profileas compared to, e.g., a standard speaker column, or a pair of speakercolumns.

The drive units 204, 205, as noted, are preferably of a nature suitablefor reproducing low and/or mid range frequencies. A plurality ofadditional smaller drive units 208 (e.g., high frequency drive units)may optionally be provided, preferably arranged in a linear array alongthe central axis between the two line arrays 214, 215 of low/midfrequency drive units (i.e., along the dividing wall 226), or elsewhere,to increase the dynamic frequency range of the speaker system.Advantageously, the sound radiated from the high frequency drive units208 emanates from approximately the same location as the low/midfrequency drive units 204, 205, so that the sound reproduction isseamless across the frequency spectrum. If necessary, slight delays canbe added to the audio signal(s) feeding the high frequency drive units208 in order to synchronize their acoustic output with the low/midfrequency drive units 204, 205.

According to one embodiment, an audio input signal for the speaker unit200 of FIGS. 2A-2B is processed in a manner providing, e.g.,frequency-independent Legendre shading, directional control, or othereffects. FIG. 4A is a high-level block diagram of circuitry forproviding audio input signals to a speaker unit such as illustrated inFIGS. 2A-2B. As shown in FIG. 4A, the sound reproduction circuitry 400includes a sound processor 401 receiving an audio input signal 441, andproviding a set of processed audio signals 407 a..n to an array ofamplifiers 440 a..n. Each of the amplifiers 440 a..n is coupled to apair of drive units, such that the first amplifier output signal 411 ais coupled to a first pair of drive units 404 a, 405 a, a secondamplifier output signal 411 b is coupled to a second pair of drive units404 b, 405 b, and so on, up until the Nth amplifier output signal 411 nbeing coupled to the last pair of drive units 404 n, 405 n. It isassumed in FIG. 4A that the drive units 404 a..n, 405 a..n correspond totheir general physical position in a speaker line array such asillustrated in FIG. 2A, and thus the drive units 404 a, 405 a would beat the “top” of the speaker line array, while drive units 404 n, 405 nwould be at the “bottom” of the speaker line array. Likewise, driveunits 404 a..n would be on the “left” of the speaker line array(corresponding to drive units 204 in FIG. 2A), while drive units 405a..n would be on the “right” of the speaker line array (corresponding todrive units 205 in FIG. 2A).

Because drive units 204, 205 directly face each other, with each pair ofopposing drive units being disposed at the same radial angle, each pairof drive units can share the same input signal—thus, for example, thefirst amplifier output signal 411 a feeds both left drive unit 404 a andright drive unit 405 a.

In operation, where the speaker line array is shaped in an arc patternsuch as depicted in FIG. 2A, the sound processor 401 may be configuredto drive each of the amplifiers 440 a..n with a different signal levelthat follows the continuous Legendre shading function, with the drivelevels gradually tapering from maximum at the center of the speaker linearray to near zero at the outer edges of the array (i.e., drive units404 a, 405 a and 404 n, 405 n). An example of such processing isdescribed in “Practical Implementation of Constant Beamwidth Transducer(CBT) Loudspeaker Circular-Arc Line Arrays,” previously incorporated byreference as if set forth fully herein. The processed drive levelsoutput from the sound processor 401 depend in part on the number ofdrive units 404 a..n, 405 a..n in the speaker system, their relativesize and spacing, the amount of truncation of the Legendre shadingfunction, and the number of discrete “steps,” if any, used toapproximate a continuous Legendre shading function.

An example is illustrated in FIG. 21. There, the continuous Legendreshading function is illustrated in dotted lines along arc 2150, with thesolid line 2151 representing the curvature of the front faceplate 237 inFIG. 2A, truncated at −12 dB. The relative positioning of the driveunits 2104 are also depicted (the drive units 2104 may be paired onopposite sides, or may be staggered, in accordance with various examplesdisclosed elsewhere herein). In general, the more drive units 2104 thatare present, the better the approximation of a continuous Legendreshading function can be achieved. Also, in general, the larger the driveunits 2104, the more difficult it will be to approximate the Legendreshading function because the fewer drive units can be utilized in thelimited space of the front arc 2151. Thus, a tradeoff generally may needto be made between the size and number of drive units 2104 in the linearray, with corresponding effect on controllability and frequency range.

The sound processing unit 401 may each comprise, for example, a digitalsignal processor (not shown) and supporting electronics. In addition toproviding Legendre shading, the sound processing units 402 may provideany necessary equalization, and may also provide signal routing and beamcontrol functions, examples of which are described in more detailhereinafter. It is also possible to obtain the shading by passive means,thereby reducing the number of amplifiers that might otherwise berequired. For example, each drive unit's sensitivity may be individuallydesigned to match that required for a particular position in the array(aided in part by either series or parallel connection of the driveunits in an opposing pair configuration). Alternatively, or in addition,a passive attenuating network may be placed between the amplifier anddrive unit, or otherwise in series therewith. Similarly, a passive delaynetwork may also be used between an amplifier and drive unit, orotherwise in series therewith, tailored to the delay required for aparticular location in the speaker line array for simulating a curvedline array.

A speaker line array configured in accordance with FIGS. 2A and 2B mayprovide various benefits and advantages over conventional CBT linearrays. For example, the speaker unit 200 may allow drive units 204, 205to be placed closer together than conventional CBT line arrays wouldallow, because the distance between the effective sound radiating areasis defined by distance between the sound output slots, not thecenter-to-center distance between the actual drive units as withconventional CBT line arrays. The sound output slots can be placedcloser together than the actual drive units of a conventional CBT linearray. The closer spacing of the effective sound radiating areas mayimprove the upper frequency response and directional control.

Another separate benefit or advantage of closer effective spacing of thesound radiating areas is that the speaker unit 200 may have a narrowprofile in terms of its relative sound radiating area (e.g., the areaalong slot 225), in comparison to, for example, a conventional CBT linearray, or other speaker line arrays.

In an example of a speaker unit 200 as may be constructed in accordancewith one embodiment, a total of 16 low/mid-frequency drive units may beprovided (eight drive units 204 in one array and eight drive units 205in the other array), the drive units 204, 205 may be selected to be 70mm in diameter, the center-to-center spacing between drive units 204 or205 in each array may be selected to be 90 mm apart, and the highfrequency drive units 208 may, for example, be approximately twice asnumerous as the number of drive units 204 or 205 in either the left orright line array, and may be spaced 45 mm center-to-center. In thisexample, the sound output slots 225 a, 225 b may be in the range of,e.g., 10-12 mm in width. These particulars are provided in the contextof a specific example, and are not meant to be limited in any manner.

A speaker unit configured in accordance with various embodiments asdisclosed above and elsewhere herein may provide, among other benefitsand advantages, wideband response along with highly constant beamwidthand directivity behavior; further, such a speaker unit may provide suchbenefits or advantages with an absence of significant side lobes.

FIGS. 3A-3B illustrate another embodiment of a speaker unit 300utilizing a form of speaker line array. The speaker unit 300 illustratedin FIGS. 3A-3B is similar to the speaker unit 200 in many respects, andreference numerals 3 xx in FIGS. 3A-3B generally correspond to analogousfeatures designated with reference numerals 2 xx in FIGS. 2A-2B. As withspeaker unit 200 in FIGS. 2A-2B, the speaker unit 300 shown in FIG. 3Ahas a pair of opposing speaker line arrays 314, 315 each comprising aseries of drive units 304, 305 (shown with dotted lines). The driveunits 304, 305 are, as before, preferably low and/or mid frequency rangedrive units, although in other embodiments they may have a differentfrequency range. The drive units 304, 305 of the two curved speakerlines arrays 314, 315 in this example are positioned facing one another,separated by a relatively narrow and elongate sound output slot 325. Theelongate sound output slot 325, which may comprise either a single slotor series of slots, runs along the length of the two opposing speakerline arrays 314, 315 and provides a path for sound to be output from thelow/mid frequency drive units 304, 305, much as described in connectionwith FIGS. 2A-2B. In this particular example, a dividing wall 326 runsdown the length of the main sound output slot 325, dividing it into twoparallel sound output slots (left and right) 325 a, 325 b. The firstsound output slot 325 a provides a path for sound to be output from thefirst speaker line array 314, and the second sound output slot 325 bprovides a path for sound to be output from the second speaker linearray 314. The drive units 304, 305 are preferably mounted on a baffleor other similar structure, in a manner acoustically isolating theirforward sound radiation from their rearward sound radiation.

The speaker unit 300 may (but need not) have two side walls 333, 334with a front faceplate 337 (which may comprise left and right sides)spanning therebetween. The speaker unit 300 may additionally have a topwallplate 332 and a bottom wallplate 331, interconnecting the side walls333, 334 and the front faceplate 337. The speaker unit 300 may also havea series of high frequency drive units 308 along the sound output slot325. Advantageously, the sound radiated from the high frequency driveunits 308 emanates from approximately the same location as the low/midfrequency drive units 304, 305, so that the sound reproduction isseamless across the frequency spectrum. If necessary, slight delays canbe added to the audio signal(s) feeding the high frequency drive units308 in order to synchronize their acoustic output with the low/midfrequency drive units 304, 305.

Unlike speaker unit 200, which has a front faceplate 337 preferablyfollowing an arc based on a continuous Legendre shading function, or atruncated portion thereof, the front faceplate 337 of the speaker unit300 in FIGS. 3A-3B is preferably substantially flat. The curvature ofthe front faceplate 227 of the embodiment shown in FIGS. 2A-2B mayinstead be simulated by electronic delays dependent upon the relativelocation of the drive units 304, 305. The drive units 304, 305 locatedin the center portion of the speaker unit 300 would have the least addeddelay (because they correspond to the location that would be closest tothe listener according to the Legendre shading function) or no delay,while the drive units 304, 305 located at the topmost and bottommostportions of the speaker unit 300 would have the most added delay(because they correspond to locations that would be furthest from thelistener according to the Legendre shading function).

FIG. 4B is a high-level block diagram of one embodiment of a circuit orsystem as may be used for providing input signals to the speaker unit300 illustrated in FIGS. 3A-3B. The sound reproduction circuitry 450illustrated in FIG. 4B is similar to the circuitry 400 shown in FIG. 4A,but adds delay to various audio output signals to simulate the curvaturealong the Legendre shading function. Similar to the system 400 of FIG.4A, the sound reproduction circuitry 450 of FIG. 4B may include a soundprocessor 451 receiving an audio input signal 491, and providing a setof processed audio signals 457 a..n to an array of amplifiers 490 a..n.Each of the amplifiers 490 a..n in this example is coupled to a pair ofdrive units, such that the first amplifier output signal 461 a iscoupled to a first pair of drive units 454 a, 455 a, a second amplifieroutput signal 461 b is coupled to a second pair of drive units 454 b,455 b, and so on, up until the Nth amplifier output signal 461 n beingcoupled to the last pair of drive units 454 n, 455 n. It is assumed inFIG. 4B that the drive units 454 a..n, 455 a..n correspond to theirgeneral physical position in a speaker line array such as illustrated inFIG. 3A, and thus the drive units 454 a, 455 a would be at the “top” ofthe speaker line array, while drive units 454 n, 455 n would be at the“bottom” of the speaker line array. Likewise, drive units 454 a..n wouldbe on the “left” of the speaker line array (corresponding to drive units304 in FIG. 3A), while drive units 455 a..n would be on the “right” ofthe speaker line array (corresponding to drive units 305 in FIG. 3A).

Because drive units 304, 305 directly face each other in the particularexample of FIG. 3A, with each pair of opposing drive units 304, 305being disposed at the same relative distance from the central axis ofthe speaker unit 300, each pair of opposing drive units can share thesame input signal—thus, for example, the first amplifier output signal461 a feeds both left drive unit 454 a and right drive unit 455 a, andso forth for the other amplifier output signals 461 b..n and drive units454 b..n, 455 b..n. Each amplifier output signal 461 a..n also has anassociated delay 471 a..n corresponding to the added distance that thesoundwaves would need to travel in air if the particular drive unit 304,305 were physically positioned along the arc of the Legendre shadingfunction, as in FIG. 2A. The amount of delay required for each driveunit 304, 305 is conceptually illustrated in FIG. 22. FIG. 22 shows ancurved speaker front on the left side thereof, having an arc based uponthe Legendre shading function as with the speaker unit 200 of FIG. 2A.The relative distance of each drive unit 204, 205 is also illustrated,with Δ1 being the differential distance from the front of the center(and hence frontmost) drive unit to the front of the topmost (and hencefurthest back) drive unit, and hence the longest distance; Δ2 being thedifferential distance from the front of the center drive unit to thefront of the second drive unit from the top (and hence the drive unitnext further back), and hence the second longest distance; and so forth.The distances Δ1, Δ2, Δ3, etc. can be readily transformed to delayquantities D1, D2, D3, etc. by calculating the length of time that itwould take soundwaves to travel those distances in air, and willgenerally be in the order of milliseconds or fractions thereof. Thedelay quantities D1, D2, D3, . . . are the same delay quantitiesDELAY-1, DELAY-2, DELAY-3, . . . applied by the circuitry in FIG. 4B, inorder to simulate the front curvature of the speaker unit 200 in FIG. 2Awith the flat-faced speaker unit 300 of FIG. 3A.

In operation, as with FIG. 2A, the sound processor 451 may be configuredto drive each of the amplifiers 490 a..n with a different signal levelthat follows the continuous Legendre shading function, with the drivelevels gradually tapering from maximum at the center of the speaker linearray to near zero at the outer edges of the array (i.e., drive units454 a, 455 a and 454 n, 455 n). As previously noted, the processed drivelevels output from the sound processor 451 depend in part on the numberof drive units 454 a..n, 455 a..n in the speaker system, their relativesize and spacing, the amount of truncation of the Legendre shadingfunction, and the number of discrete “steps,” if any, used toapproximate a continuous Legendre shading function. In addition, thedelay quantities introduced by delays 471 a..n are cumulative to theprocessing carried out by the sound processor 451.

While delays 471 a..n are shown conceptually as separate blocks in FIG.4B, it should be understood that the delays 471 a..n may be implementedin any of a variety of manners—for example, using hardware delays (whichmay be tunable), or by using programming the delays using digital signalprocessing that may be incorporated in the sound processor 451. Thedelay circuit may thus take the form of any suitable electroniccircuitry (either active or passive, and either analog or digital), andpreferably have minimal or no impact on the content of the audio outputsignal, at least over the frequencies being reproduced.

FIG. 5 illustrates another embodiment of a speaker unit 500 configuredas a speaker line array. The speaker unit 500 illustrated in FIG. 5 issimilar to the speaker unit 300 shown in FIGS. 3A-3B in many respects;thus, reference numerals 5 xx in FIG. 5 generally correspond toanalogous features designated with reference numerals 3 xx used in FIGS.3A-3B. As with speaker unit 300 in FIGS. 3A-3B, the speaker unit 500shown in FIG. 5 has a pair of opposing speaker line arrays 514, 515,each comprising a series of drive units 504, 505 (shown with dottedlines). The main difference over the speaker unit 300 of FIGS. 3A-3B isthat the drive units 504 of speaker unit 500 in FIG. 5 are staggeredwith respect to the opposing drive units 505. A particular advantage ofthe speaker unit 500 of FIG. 5 is that a more graduated Legendre shadingeffect can be achieved, because the intervals between the drive units504, 505 are effectively cut in half, and so reduces spatial aliasing.Spatial aliasing is a known phenomenon described in more detail, forexample, in R. Schmidmaier and D. G. Meyer, “Dynamic Amplitude Shadingof Electronically Steered Line Source Arrays,” 92^(nd) Convention of theAudio Engineering Society, Preprint 3272 (Mar. 24-27, 1992), herebyincorporated by reference as if set forth fully herein. As generallyexplained therein, for a given spacing d of acoustical sources, nospatial aliasing occurs (and therefore no grating lobes are produced)for frequencies f below f=c/2d, where c is the velocity of sound.Therefore, reducing the spacing between drive units by means ofstaggering their relative positions in opposing slots may advantageouslyincrease the first frequency at which spatial aliasing occurs along theaxis of the array. Similarly, the ability to space the drive units closetogether by placing them face-to-face, for example, may advantageouslyreduce the effect of lobes perpendicular to the slot axis. The speakerunit 500 of FIG. 5 may require some additional processing because theoutput signals to opposing drive units can no longer be shared.

In other respects, the speaker unit 500 is very similar to that of FIGS.3A-3B. The drive units 504, 505 are, as before, preferably embodied aslow and/or mid frequency range drive units, although they may also covera different frequency range. The drive units 504, 505 are, as notedabove, positioned facing one another but staggered, and are separated bya relatively narrow and elongate sound output slot 525. The elongatesound output slot 525 may comprise either a single slot or series ofslots, and runs along the length of the two opposing speaker line arrays514, 515, providing a path for sound to be output from the low/midfrequency drive units 504, 505 as described previously with respect tothe other similar speaker units. In this particular example, a dividingwall 526 runs down the length of the main sound output slot 525,dividing it into two parallel sound output slots (left and right) 525 a,525 b. As with the previously described speaker units, the first soundoutput slot 525 a provides a path for sound to be output from the firstspeaker line array 514, and the second sound output slot 525 b providesa path for sound to be output from the second speaker line array 515.The drive units 504, 505 are preferably mounted on a baffle or othersimilar structure, in a manner acoustically isolating their forwardsound radiation from their rearward sound radiation. The speaker unit500 may also have high frequency drive units 508 running down the lengthof the main output slot 525. Advantageously, the sound radiated from thehigh frequency drive units 508 emanates from approximately the samelocation as the low/mid frequency drive units 504, 505, so that thesound reproduction is seamless across the frequency spectrum. Ifnecessary, slight delays can be added to the audio signal(s) feeding thehigh frequency drive units 508 in order to synchronize their acousticoutput with the low/mid frequency drive units 504, 505.

The speaker unit 500 may (but need not) have two side walls 533, 534with a front faceplate 537 (which may comprise left and right sides)spanning therebetween. The speaker unit 500 may additionally have a topwallplate 532 and a bottom wallplate 531, interconnecting the side walls533, 534 and the front faceplate 537. The speaker unit 500 alsopreferably has acoustic absorbing material, similar to as shown in FIG.3B, around the rear contours of the drive units 504, 505 to force thesoundwaves out of the output slot 525, and to reduce, e.g., turbulenceand/or standing waves that may otherwise arise.

A particular speaker unit embodiment constructed in accordance with thegeneral principles of FIG. 5 is illustrated in FIGS. 13A (front view)and 13B (cross sectional front view). As depicted therein, a speakerunit 1300 includes two speaker line arrays facing one another and eachhaving eight low or mid frequency drive units 1304, 1305 in use (shownin solid in FIG. 13B), staggered with respect to the drive units on theopposing line array. An array of sixteen high frequency drive units 1308(shown in solid in FIG. 13A) are positioned down the middle of thespeaker unit 1300. The low/mid frequency drive units 1304, 1305 radiateacoustically from sound output slots 1325 a, 1325 b, as described above.

Sound processing for speaker unit 500 (or 1300) is similar to thatcarried out for speaker unit 300 of FIGS. 3A-3B, but because the driveunits 504, 505 are staggered additional components may be needed. FIG. 6is a high-level block diagram depicting an embodiment of circuitry asmay be used for providing input signals to the speaker unit 500illustrated in FIG. 5. The sound reproduction circuitry 600 illustratedin FIG. 6 is similar to the circuitry 450 shown in FIG. 4B, but includesa separate output signal and delay for each drive unit 504, 505(depicted as 604 a..n, 605 a..n in FIG. 6). As before the delays 671have the effect of simulating the curvature along the Legendre shadingfunction. Similar to the circuitry 450 of FIG. 4B, the soundreproduction circuitry 600 of FIG. 6 may include a sound processor 601receiving an audio input signal 641, and providing a set of processedaudio signals 607 a 1,2..n 1,2 to an array of amplifiers 640 a 1,2..n1,2. Each of the amplifiers 640 a 1,2..n 1,2 in this example is coupledto a single drive unit, such that the first amplifier output signal 611a 1 is coupled to a first left drive unit 604 a, a second amplifieroutput signal 611 a 2 is coupled to a first right drive units 605 a, athird amplifier output signal 611 b 1 is coupled to a second left driveunit 604 b, a fourth amplifier output signal 611 b 2 is coupled to asecond right drive unit 605 b, and so on, up until the Nth pair ofamplifier output signals 611 n 1,2 being coupled to the last pair ofdrive units 604 n, 605 n.

It is assumed in FIG. 6 that the drive units 604 a..n, 605 a..ncorrespond to their general physical position in a speaker line arraysuch as illustrated in FIG. 5, and thus the drive units 604 a, 605 awould be at the “top” of the speaker line array, while drive units 604n,6055 n would be at the “bottom” of the speaker line array. Likewise,drive units 604 a..n would be on the “left” of the speaker line array(corresponding to drive units 504 in FIG. 5), while drive units 605 a..nwould be on the “right” of the speaker line array (corresponding todrive units 505 in FIG. 5).

Similar to the speaker unit 300 and associated processing in FIG. 4B,each amplifier output signal 611 a 1,2..n 1,2 also has an associateddelay 671 a 1,2..n 1,2 corresponding to the added distance that thesoundwaves would need to travel in air if the particular drive unit 504,505 were physically positioned along the arc of the Legendre shadingfunction, as in FIG. 2A. The amount of delay required for each driveunit 504, 505 is calculated as before, described with respect to FIG.22.

Although the speaker unit 500 and associated processing has beendescribed in relation to a flat-front speaker unit (similar to speakerunit 300 of FIGS. 3A-3B), the same technique of staggering drive units504, 505 may also be applied in other embodiments, such as thecurved-face speaker unit 200 of FIGS. 2A-2B.

A speaker line array configured in accordance with FIG. 5 may providevarious benefits and advantages over conventional CBT line arrays andother speaker line arrays. For example, the speaker unit 500 may allowdrive units 504, 505 to be placed effectively closer together than,e.g., conventional CBT line arrays or other line arrays withoutstaggered drive units. The closer effective spacing of the drive units504, 505 may improve the upper frequency response and directionalcontrol. This effect can be explained in more detail with reference toFIG. 23, which compares certain characteristics of a conventional linearray 2310 using non-staggered drive units with a (slotted) dual linearray speaker unit 2320 having staggered drive units. The overall lengthD of the line array 2310 determines the lowest frequency that can bereproduced. The length D is preferably sufficiently long to generate thedesired lowest frequency. On the other hand, the spacing d between thedrive units 2311 in the line array 2310 determines the maximum frequencythat can be reproduced. Thus, minimizing the spacing d can be quiteimportant to achieving acceptable high frequency response. While usingsmaller drive units 2311 may reduce the spacing d, doing so maynegatively impact the ability to reproduce bass tones. On the otherhand, using too large drive units 2311 may make d so large that highfrequency response may be unacceptable. By contrast, the staggered driveunits 2321, 2322 of the dual line array speaker unit 2320 effectivelycuts distance d in half, thereby effectively doubling the maximumfrequency that can be output without negatively affecting reproductionof the bass tones. By further making the two speaker line arraysslotted, as in FIG. 5, the effective radiating areas of the drive units2321, 2322 can be brought closer together, minimizing the impact ofhaving the drive units 2321, 2322 separated into two separate linearrays. Thus, overall the combination of the staggered drive units 2321,2322 and the slotted output allows, among other things, optimal soundreproduction with a frequency range that is significantly greater thanhas been heretofore possible.

Another separate benefit or advantage is that the speaker unit 500 mayhave a narrow profile in terms of its relative sound radiating area(e.g., the area along slot 525), in comparison to, for example, aconventional CBT line array, or other speaker line arrays.

In some cases, it may be desired to have a narrower total width of thesound output slot 325 or 525 than the width of the high frequency driveunits 308 or 508. For example, the high frequency drive units 308, 508may be about 20 millimeters in width, which in some cases may be largerthan desired. By placing the high frequency drive units 308, 508slightly forward of the sound output slot 325, 525, the high frequencydrive units 308, 508 may be wider than the sound output slot 325, 525 ifdesired. It may be desirable in such a situation to add a slight delayto the signal driving the high frequency drive units 308, 508 so thattheir output is synchronized with the low/mid frequency drive units, ifthe slight difference in output is noticeable.

In certain instances it may be desirable to increase the effectivemaximum frequency of the high frequency drive units 308 or 508 bystaggering the high frequency drive units, using similar principles asdescribed with respect to the low/mid frequency drive units in FIGS.3A-3B and 5. The high frequency drive units 308, 508 may also bepositioned sideways with respect to the front face of the speaker unitand paired, like the low/mid frequency drive units in FIGS. 3A-3B, suchthat their output is conveyed via a slot similar to the low/midfrequency drive units also. In addition, it is possible to extend theprinciples described herein from a two-way speaker system to a three-wayspeaker system, by providing separate line arrays for low frequencydrive units, mid-frequency drive units, and high frequency drive units,respectively.

The high frequency drive units in any of the embodiments herein may beconstructed with a speaker cone or else may, for example, be isodynamicin nature. While isodynamic drive units may have low distortion and alarge radiating area, they may, depending upon their construction, havecertain disadvantages (such as lower efficiency) and may be moreexpensive than other types of drive units.

A particular embodiment of a speaker unit with staggered drive unitsconfigured according to principles described with respect to FIGS. 5 and6, is illustrated from various viewpoints and cross-sections in FIGS.19A-19D. In general, reference numerals 19 xx represent features inFIGS. 19A-19D similar to those identified with reference numerals 5 xxin FIG. 5. As shown first in FIG. 19A, a speaker unit 1900 may comprisean enclosure formed of a substantially flat faceplate 1937 (split intoleft and right sides in FIG. 19A), sidewalls 1933, 1934, a basewallplate 1931, a top wallplate 1932, and a backplate 1995 (as shown inFIGS. 19B-19D). The speaker unit 1900 in this example includes speakerline arrays 1914, 1915 which are depicted in FIGS. 19C (showing a crosssection taken along line A-A in FIG. 19A) and 19D (showing a crosssection taken along line C-C in FIG. 19A), respectively, each speakerline array 1914, 1915 comprising an array of drive units 1904, 1905. Thedrive units 1904, 1905, as with FIG. 5, are preferably embodied as lowand/or mid frequency range drive units, although they may also cover adifferent frequency range. The drive units 1904, 1905 are positionedfacing one another, but staggered, and are separated by a relativelynarrow and elongate sound output slot 1925. The elongate sound outputslot 1925 may comprise either a single slot or series of slots, and runsalong the length of the two opposing speaker line arrays 1914, 1915,providing a path for sound to be output from the low/mid frequency driveunits 1904, 1905 as described previously with respect to FIG. 5 andother speaker units disclosed herein.

As further illustrated in FIG. 19A, an array of high frequency driveunits 1908 may be positioned down the length of the main output slot1925. Advantageously, the sound radiated from the high frequency driveunits 1908 emanates from approximately the same location as the low/midfrequency drive units 1904, 1905, so that the sound reproduction isseamless across the frequency spectrum. If necessary, slight delays canbe added to the audio signal(s) feeding the high frequency drive units1908 in order to synchronize their acoustic output with the low/midfrequency drive units 1904, 1905. In this particular example, a dividingwall 1926 runs down the length of the main sound output slot 1925,dividing it into two parallel sound output slots (left and right) 1925a, 1925 b. As with the previously described speaker units, the firstsound output slot 1925 a provides a path for sound to be output from thefirst speaker line array 1914, and the second sound output slot 1925 bprovides a path for sound to be output from the second speaker linearray 1915.

Further details of the internals of the speaker unit are depicted inFIG. 19B, which is a cross-sectional view of the speaker unit 1900 takenalong line B-B in FIG. 19A. As shown therein, a high frequency driveunit 1908 is positioned between the two sides of the front faceplate1937, in approximately the same plane therewith (although this is notnecessarily required). A left drive unit 1904 from the first speakerline array 1914 is mounted on a baffle 1988 (or other similar structure)which acoustically isolates the drive unit's forward sound radiationfrom its rearward sound radiation. Similarly the right drive unit 1905is also mounted on a baffle 1989 (or other similar structure) whichacoustically isolates the drive unit's forward sound radiation from itsrearward sound radiation. The baffles 1988, 1989 are also illustrated inFIGS. 19C and 19D. As best depicted in those two figures, the speakerunit 1900 also preferably has acoustic absorbing material (such ascompressed foam) 1939 a, 1939 b which is shaped so as to force the soundwaves out of the output slot 1925 a or 1925 b, and to reduce undesiredeffects such turbulence and/or standing waves that may otherwise arise.In this particular example, the acoustic absorbing material 1939 a, 1939b is shaped so as to separate or isolate each of the drive units 1904,1905 from the adjacent drive units. It is also shaped so that it expandstowards the opening of the sound output slot 1925 a or 1925 b, and sothat it generally follows the rear contours of the drive unit cones. Theacoustic absorbing material 1939 a, 1939 b is also depicted between thebaffles 1988, 1989 in FIG. 19B, along with additional central sectionsof cut foam (or other similar acoustic absorbing material) 1997, 1998which collectively form the dividing wall 1926 shown in FIG. 19A.

Because the drive units 1904, 1905 are staggered with respect to eachline array 1914, 1915, the slot openings are likewise staggered. Thus,in FIG. 19B, the slot opening 1925 b drive unit 1905 is illustrated, butat that particular cross-section the acoustic absorbing material 1939 adivides two of the left drive units 1904 and thus appears to reach tothe edge of where the left side output slot 1925 a would be. If thecross section were taken slightly further up or down in the speaker unit1900, the opposite situation would occur; that is, the acousticabsorbing material 1939 b on the right hand side would appear to reachthe each of the right side output slot 1925 b, while the left sideoutput slot 1925 would be visible.

The width of the acoustic absorbing material 1939 a, 1939 b in thisexample generally corresponds to the width of the left and right outputslots 1925 a, 1925 b, although in other embodiments the acousticabsorbing material could be shaped or contoured as desired. In oneembodiment, for example, the acoustic absorbing material 1939 a, 1939 bis about 10 to 12 millimeters thick; this thickness may affect themaximum desirable frequency output. In addition, acoustic dampingmaterial 1984 such as BAF wadding (which is a soft, synthetic acousticdamping material) may be placed in the enclosures between the baffles1988, 1989 and the respective sidewalls 1934, 1933. Other features, suchas gasket strips 1976, 1993 in FIG. 19B, and gaskets 1909 in FIG. 19Aare also illustrated.

In the exemplary speaker unit 1900 illustrated in FIGS. 19A-19D, a totalof 17 staggered low/mid frequency drive units 1904, 1905 are used, aswell as 17 high frequency drive units 1908. However, any number of driveunits 1904, 1905 or 1908 may be used to suit a particular application orneed.

The sound processing for the speaker unit 1900 may be similar to thatfor FIG. 5; in other words, a sound processor constructed in accordancewith FIG. 6 may be suitable to provide sound output for the speaker unit1900.

Another generally similar embodiment of a speaker unit with staggereddrive units configured according to some of the principles describedwith respect to FIGS. 5 and 6, and 19A-D, is illustrated from variousviewpoints and cross-sections in FIGS. 20A-20E. The speaker unit inFIGS. 20A-20D is similar to speaker unit 1900 in FIGS. 19A-19D, but thedrive units 2004, 2005 are reversed in orientation so that rather thanfacing one another they are facing away from each other. FIGS. 20A-20Dare aligned so that the various features of the speaker unit areillustrated at the same relative position across the four figures,although the entire speaker enclosure is not illustrated. As shown inFIG. 20A, the speaker unit in this embodiment includes two adjacentspeaker line arrays 2014, 2015 each comprising a set of drive units2004, 2005. The drive units 2004, 2005 are preferably embodied as lowand/or mid frequency range drive units, although they may also cover adifferent frequency range. The drive units 2004, 2005 are positionedfacing away from one another, and are staggered so that the speaker linearrays 2014, 2015 can be closer together. Similar to the other speakerunits, the drive units 2004, 2005 provide their acoustic radiation outof sound output slots 2025 a, 2025 b, which in this example are embodiedas a series of slots (one for each drive unit 2004, 2005) although asingle output slot, or shared output slots, may be used as well. Thesound output slots 2025 a, 2025 b provide a path for sound to be outputfrom the low/mid frequency drive units 2004, 2005 as described withrespect to various other speaker units disclosed herein. The soundoutput slots 2025 a, 2025 b may be constructed as part of a drive unitwaveguide module 2081 a or 2081 b, as further described below.

As further illustrated in FIGS. 20A and 20D, an array of high frequencydrive units 2008 may be positioned down the length of the center of thespeaker unit, between the speaker line arrays 2014, 2015.Advantageously, the sound radiated from the high frequency drive units2008 emanates from near the same location as the low/mid frequency driveunits 2004, 2005, although not as close as the speaker unit 1900 ofFIGS. 19A-19D. If necessary, slight delays can be added to the audiosignal(s) feeding the high frequency drive units 2008 in order tosynchronize their acoustic output with the low/mid frequency drive units2004, 2005. A front faceplate 2037 (which may have slight contours,ridges, or the like for aesthetic purposes) is positioned in front ofthe speaker line arrays 2014, 2015. A foam or other sound-permeablecover 2080 may be disposed in front of the front faceplate 2037.

Further details of the internals of the speaker unit are depicted inFIGS. 20D, 20E and 20F. FIG. 20E depicts two different side views of adrive unit waveguide module 2081, showing the relative orientation ofthe sound output slot 2025 a (or 2025 b) with respect to the drive unit2004 (or 2005). The drive unit waveguide module 2081 may include, forexample, a mounting baffle and acoustic absorbing material surroundingthe outer contours of the drive unit 2004 (or 2005) thereby directingthe acoustic radiation from the drive unit to the sound output slot 2025a (or 2025 b). FIG. 20D illustrates an array of drive unit waveguidemodules 2081 positioned in a manner forming a speaker line array (2014or 2015). FIG. 20D further illustrates the positioning of high frequencydrive units 2008 in front of the drive units 2004 (or 2005). As analternative to separate mounting baffles and acoustic absorbing materialfor each drive unit, a common mounting baffle and acoustic absorbingmaterial may be used for the drive units, as illustrated in FIGS.19C-19D, for example.

FIG. 20F shows a top cross-sectional view of the speaker unit, with apair of staggered drive units 2004, 2005 oriented facing away from eachother. The drive units 2004, 2005 are mounted on baffles 2088, 2089,respectively, which preferably serve to acoustically isolate each of thedrive unit's forward sound radiation from its rearward sound radiation.In the cross sectional view shown, the sound output slot 2025 a for theleft drive unit 2004 is illustrated, with acoustic absorbing material(e.g., compressed foam) 2039 a shown enclosing the sound output slot2025 a. Because of the staggering of the drive units 2004, 2005, thesound output slot 2025 b for drive unit 2005 is not visible, but ratherthe acoustic absorbing material 2039 b which defines the sides of thesound output slot 2025 b is shown extending to the front faceplate 2037.In addition, acoustic damping material 1984 such as BAF wadding, may beplaced as filler behind the drive units 2004, 2005. The high frequencydrive unit 2008 is also illustrated in a position between the two driveunits 2004, 2005.

In the exemplary speaker unit illustrated in FIGS. 20A-20E, a total of17 staggered low/mid frequency drive units 2004, 2005 are shown, inaddition to 35 high frequency drive units 2008. However, any number ofdrive units 2004, 2005 or 2008 may be used to suit a particularapplication or need.

The sound processing for the speaker unit in FIGS. 20A-20E may begenerally similar to that for FIG. 5; in other words, a sound processorconstructed in accordance with FIG. 6 may be suitable to provide soundoutput for such a speaker unit.

FIG. 7 illustrates another embodiment of a speaker unit 700 configuredaccording to principles of a speaker line array. The speaker unit 700illustrated in FIG. 7 is similar to the speaker unit 200 shown in FIGS.2A-2B in many respects; thus, reference numerals 7 xx in FIG. 7generally correspond to analogous features designated with referencenumerals 2 xx used in FIGS. 2A-2B. As with speaker unit 200 in FIGS.2A-2B, the speaker unit 700 shown in FIG. 7 has a pair of opposingspeaker line arrays 714, 715, each comprising a series of drive units704, 705 (shown with dotted lines). A primary difference over thespeaker unit 200 of FIGS. 2A-2B is that the speaker unit 700 is only theupper half of a full speaker unit, but in other respects the speakerunit 700 has a similar configuration, operation, and electronics (e.g.,as shown in FIG. 4A, but with only half of the amplifiers to serve thereduced number of drive units).

The speaker unit 700 comprises two curved speaker line arrays 714, 715,in the general shape of a semi-arc, each line array 714, 715respectively comprising a series of drive units 704, 705 (shown withdotted lines). The drive units 704, 705, as before, are preferably, butneed not be, low and/or mid frequency range drive units. Similar to thespeaker unit 200 of FIGS. 2A-2B, the drive units 704, 705 of the twocurved speaker lines arrays 714, 15 in this example are positionedfacing one another, separated by a relatively narrow and elongate soundoutput slot 725. The elongate sound output slot 725 provides a path forsound to be output from the drive units 704, 705. In this particularexample, a dividing wall 726 runs down the length of the main soundoutput slot 725, dividing it into two parallel sound output slots (leftand right) 725 a, 725 b. The first sound output slot 725 a provides apath for sound to be output from the first speaker line array 714, andthe second sound output slot 725 b provides a path for sound to beoutput from the second speaker line array 715. The drive units 704, 705are preferably mounted on a baffle or other similar structure, in amanner acoustically isolating their forward sound radiation from theirrearward sound radiation. The speaker unit 700 may also have highfrequency drive units 708 running down the length of the main outputslot 725. Advantageously, the sound radiated from the high frequencydrive units 708 emanates from approximately the same location as thelow/mid frequency drive units 704, 705, so that the sound reproductionis seamless across the frequency spectrum. If necessary, slight delayscan be added to the audio signal(s) feeding the high frequency driveunits 708 in order to synchronize their acoustic output with the low/midfrequency drive units 704, 705.

The speaker unit 700 may have two side walls 733, 734 with a curvedfront faceplate 737 (which may comprise left and right sides) spanningtherebetween. The curvature of the front faceplate 737 preferablyfollows the upper portion of an arc based on a continuous Legendreshading function, or a truncated portion thereof, as previouslydescribed with respect to FIGS. 2A-2B. The speaker unit 700 mayadditionally have a top wallplate 732 and a bottom wallplate 731, eachinterconnected to the side walls 733, 734 and the front faceplate 737.Although not shown in the illustration, acoustic absorbing material(e.g., compressed foam) is placed circumjacent to the outer rearcontours of the drive units 704, 705, similar to FIG. 2B, to provide arear barrier and thereby force the sound to be projected from the soundoutput slot 725. The drive units 704, 705 may be driven by electronicssimilar to the circuitry 400 illustrated in FIG. 4A, but with only theportion thereof needed for the upper half of the speaker unit 200illustrated in FIGS. 2A-2B.

In operation, the speaker unit 700 functions similarly to the speakerunit 200 shown in FIGS. 2A-2B. However, when the speaker unit 700 isplaced on an acoustically reflective surface (a ground plane), the lowerhalf of the Legendre arc is effectively “restored” by the soundreflecting from the drive units 704, 705 and 708 on the reflectivesurface, providing that the listening distance is sufficiently far, aswill typically be the case. Speaker unit 700 has the advantage of beingsmaller in size than other speaker line arrays, and using fewer driveunits and electrical components than may otherwise be needed.

In other embodiments, speaker unit 700 could be substantially flat, withaudio processing and/or delays to simulate the Legendre curvaturesimilar to the speaker units illustrated in FIGS. 3A-3B and 5, or orderto achieve a similar effect. In these embodiments, the upper half of thespeaker unit such as illustrated in FIG. 3A-3B or 5 would be utilized,and the speaker unit placed on a hard or reflective surface.Alternatively, or in addition, the drive units 704, 705 in speaker unit700 may be staggered with respect to one another, as with speaker unit500 of FIG. 5. In such a configuration, which essentially corresponds toa full staggered speaker arrangement such as shown in FIG. 5 being “cutin half,” the reflection in the ground plane will be incomplete due tothe absence of a half drive unit in the bottom position of one side(either left or right) of the line array. To overcome this absence andmost closely simulate a full-sized staggered speaker arrangement such asshown in FIG. 5, a phantom drive unit can be created by modifying thedrive signal fed to the bottom-most drive unit in the line array, so asto create a phantom sound image of the missing drive unit. For example,supposing that the left array was “missing” the (half) drive unit at thebottom of the line array, a phantom image corresponding to the missingdrive unit could be created by feeding a signal corresponding toone-half of the Legendre shading function value to the bottom-most driveunit on the right array, which is the closest drive unit to the groundplane. Due to the reflection from the ground plane, the one-halfstrength signal is doubled thus roughly approximating a drive unit(i.e., a phantom drive unit) centered on the ground plane. While notnecessarily being identical to having a physical drive unit centered atthe ground plane, this technique should result in a relatively goodapproximation thereof. Note that in order to have the phantom imageproperly integrated into the Legendre shading function, the signals tothe other drive units need to be appropriately delayed with respect tothe phantom drive unit, treating it as if it were a real drive unit.

FIG. 8 illustrates another embodiment of a speaker unit 800 configuredaccording to principles of a speaker line array. The speaker unit 800illustrated in FIG. 8 is similar to several of the previously describedspeaker units, and in certain respects may be viewed as a hybrid of thespeaker unit 200 shown in FIGS. 2A-2B and the speaker unit 300illustrated in FIGS. 3A-3B. Thus, reference numerals 8 xx in FIG. 8generally correspond to analogous features designated with referencenumerals 2 xx used in FIGS. 2A-2B and/or 3 xx in FIGS. 3A-3B. Similar tospeaker unit 200 in FIGS. 2A-2B, the speaker unit 800 shown in FIG. 8has a pair of opposing speaker line arrays 814, 815, each comprising aseries of drive units 804, 805 (shown with dotted lines). The centralpart 896 of the speaker unit 800 is curved in the same manner as thespeaker unit 200 in FIGS. 2A-2B; however, the upper and lower parts 897,898 of the speaker unit 800 are substantially flat. The drive units 804,805 which are in the central part 896 of the speaker unit 800 mayoperate in a similar manner to the drive units of speaker unit 200,while the drive units 804, 805 in the upper and lower parts 897, 898 ofthe speaker unit 800 may operate in a similar manner to the drive unitsof speaker unit 300—that is, using electronic delay processing tosimulate the upper and lower arced portions of the Legendre curvature(as described with respect to FIG. 4B). Alternatively, the drive units804, 805 may not have added electronic delay processing to simulateLegendre curvature; although this may slightly reduce the advantagesprovided by the Legendre shaping, the difference may not be significantdepending on the extent of truncation.

In one embodiment, the curved central portion 896 of the speaker unit800 is “truncated” where the flat upper and lower portions 897, 898begin. As a result, the overall depth of the speaker unit 800 is not asgreat as that of speaker unit 200, for example, which has a fully curvedfront face. The speaker unit 800 may therefore have certain packagingadvantages, and may resemble to a greater degree a conventional flatspeaker unit from an exterior physical or aesthetic standpoint. Incertain embodiments, the speaker unit 800 may also have increasedphysical stability over speaker unit 200 in FIG. 2, and/or may use fewerelectronic components or operate with simpler audio processing.

As with the other speaker line arrays, the drive units 804, 805 arepreferably, but need not be, low and/or mid frequency range drive units.Similar to the speaker units of FIGS. 2A-2B and 3A-3B, the drive units804, 805 of the speaker lines arrays 814, 815 may be positioned facingone another, separated by a relatively narrow and elongate sound outputslot 825 which provides a sound output path. A dividing wall 826 may rundown the length of the main sound output slot 825, dividing it intoparallel sound output slots 825 a, 825 b, providing paths for sound tobe output from the first and second speaker line arrays 814, 815,respectively. The drive units 804, 805 are preferably mounted on abaffle or other similar structure, in a manner acoustically isolatingtheir forward sound radiation from their rearward sound radiation. Thespeaker unit 800 may also have high frequency drive units 808 runningdown the length of the main output slot 825. As noted previously, thesound radiated from the high frequency drive units 808 will emanate fromapproximately the same location as the low frequency drive units 804,805, so that the sound reproduction is seamless across the frequencyspectrum. If necessary, slight delays can be added to the audiosignal(s) feeding the high frequency drive units 808 in order tosynchronize their acoustic output with the low/mid frequency drive units804, 805.

The speaker unit 800 may have two side walls 833, 834 with a curvedcenter front faceplate 837 (which may comprise left and right sides), anupper front faceplate 857, and lower front faceplate 858 spanningtherebetween. The curvature of the front faceplate 837 preferablyfollows the central portion of an arc based on a continuous Legendreshading function, or a truncated portion thereof, as previouslydescribed with respect to FIGS. 2A-2B. The speaker unit 800 mayadditionally have a top wallplate 832 and a bottom wallplate 831,interconnected to the side walls 833, 834 and the front faceplates 837,857, 858. Although not shown in the illustration, acoustic absorbingmaterial (e.g., compressed foam) is placed circumjacent to the outerrear contours of the drive units 804, 805, similar to FIG. 2B or 3B, toprovide a rear barrier and thereby force the sound to be projected fromthe sound output slot 825.

In operation, the central portion 896 of the speaker unit 800 functionssimilarly to the speaker unit 200 shown in FIGS. 2A-2B, while the upperand lower portions 897, 898 of the speaker unit 800 may functionsimilarly to speaker unit 300 illustrated in FIGS. 3A-3B. In such anexample, the electronics for speaker unit 800 may be configured, forexample, according to the sound reproduction circuitry 900 illustratedat a high block level in FIG. 9. It is assumed in FIG. 9 that the driveunits 904 a..i, 905 a..i correspond to their general physical positionin a speaker line array such as illustrated in FIG. 8, and thus thedrive units 904 a, 905 a would be at the “top” of the speaker linearray, while drive units 904 i, 905 i would be at the “bottom” of thespeaker line array. Likewise, drive units 904 a..i would be on the“left” of the speaker line array (corresponding to drive units 904 inFIG. 8), while drive units 905 a..i would be on the “right” of thespeaker line array (corresponding to drive units 905 in FIG. 9). Forpurposes of explanation and illustration, the particular example of FIG.9 uses nine pairs of drive units 904 a..i, 905 a..i, with five pairs ofdrive units 904 c..g, 905 c..g located in the central portion of thespeaker unit 800 and two pairs of drive units (904 a, 904 b and 905 a,905 b being the first pair, and 904 h, 904 i and 905 h, 905 i being thesecond pair) being located in the upper and lower portions,respectively, of the speaker unit 800. However, the principles describedwith respect to FIG. 9 may be extended to additional pairs of driveunits as well.

The circuitry 900 illustrated in FIG. 9 is a hybrid of the circuitry 400shown in FIG. 4A and the circuitry 450 shown in FIG. 4B. Thus, similarto the system 400 of FIG. 4A, the sound reproduction circuitry 900 mayinclude a sound processor 901 receiving an audio input signal 941, andproviding a set of processed audio signals 907 a..i to an array ofamplifiers 940 a..i. Each of the amplifiers 940 a..i in this example iscoupled to a pair of drive units, such that the first amplifier outputsignal 911 a is coupled to a first pair of drive units 904 a, 905 a, asecond amplifier output signal 911 b is coupled to a second pair ofdrive units 904 b, 905 b, and so on, up until the i^(th) amplifieroutput signal 911 i being coupled to the last pair of drive units 904 i,905 i.

Because drive units 804, 805 directly face each other in the particularexample of FIG. 8, with each pair of opposing drive units 804, 805 beingdisposed at the same relative distance (and at the same relative angle)from the central plane of the speaker unit 800, each pair of opposingdrive units can share the same input signal—thus, for example, the firstamplifier output signal 911 a feeds both left drive unit 904 a and rightdrive unit 905 a, and so forth for the other amplifier output signals911 b..i and drive units 904 b..i, 905 b..i. The amplifier outputsignals 911 a, 911 b, 911 h, 911 i feeding the drive units in the upperand lower portions of the speaker array may also has an associated delay971 a, 971 b, 971 h, 971 i corresponding to the added distance that thesoundwaves would need to travel in air if the particular drive unit 904a, 904 b, 904 h, 904 i, 905 a, 905 b, 905 h, or 905 i were physicallypositioned along the arc of the Legendre shading function, as in FIG.2A. The amount of delay required for each drive unit is the same asexplained previously with respect to FIGS. 4B and 22.

In operation, as with the circuitry in FIGS. 4A and 4B, the soundprocessor 901 may be configured to drive each of the amplifiers 940 a..iwith a different signal level that follows the continuous Legendreshading function, with the drive levels gradually tapering from maximumat the center plane of the speaker line array (i.e., drive units 904 e,905 e) to near zero at the outer edges of the array (i.e., drive units904 a, 905 a and 904 i, 905 i). As before, the processed drive levelsoutput from the sound processor 901 depend in part on the number ofdrive units 904 a..i, 905 a..i in the speaker system, their relativesize and spacing, the amount of truncation of the Legendre shadingfunction, and the number of discrete “steps,” if any, used toapproximate a continuous Legendre shading function. In addition, thedelay quantities introduced by delays 971 a, 971 b, 971 h, 971 i arecumulative to the processing carried out by the sound processor 901.

While delays 971 a, 971 b, 971 h, 971 i are shown conceptually asseparate blocks in FIG. 9, it should be understood that they may beimplemented in any of a variety of manners—for example, using hardwaredelays (which may be tunable), or by using programming the delays usingdigital signal processing that may be incorporated in the soundprocessor 901.

In other embodiments, the drive units 804, 805 of the speaker unit 800may be staggered (similar to FIG. 5), with appropriate modification tothe audio circuitry (similar to FIG. 6), or else may be a “half” unitsuch as described with respect to FIG. 7.

A sound reproduction system constructed in accordance with any of theembodiments illustrated in FIG. 2A-2B, 3A-3B, 5, 7, 8, 19A-D, or 20A-F,having a plurality of drive units arranged in a column or array, mayprovide a number of potential benefits or advantages over conventionalspeaker arrays or systems. For example, such a sound reproduction systemmay provide improved steerability, directional control, width control,and/or beam overlay capability. Some of these benefits and advantagesare further explained below, in connection with various featuresrelating to audio electronics and processing as may be used to drive orcontrol the speaker units.

In certain embodiments, a speaker unit may be configured with anamplifier output stage integrated or collocated with the speaker unit,while the first stage of the amplifier is located remotely. The firststage of the amplifier may be embodied as part of an audio control unitwhich also includes command and power distribution capability. Commandand/or power signals may be communicated from an audio control unit toone or more speaker units, such as speaker line arrays, which may belocated at different physical locations. The speaker unit's amplifieroutput stage may be embodied as part of a local audio processing unitthat is based on, e.g., one or more digital signal processors (DSPs)which receive and respond to the signals sent from the remote audiocontrol unit. The command and power signals may control the speaker unitso as to provide a directional or steerable sound image, with one ormore audio beams, and/or to create one or more real phantom speakerimages, as further described herein. The control signals may betransmitted in any suitable format—for example, in analog form (as,e.g., pulse width modulated (PWM) signals) or as binary digital signals.The communication path between the remote audio control unit and thespeaker unit's audio processing unit may be two-way in nature. Inaddition to controlling the output of the speaker unit, the remote audiocontrol unit may also be able to calibrate the individual speaker units,at initial setup or before a particular audio program, using for exampleindividual codes associated with each speaker unit. In one aspect, anintelligent controllable speaker is provided, according to certainembodiments as disclosed herein.

The power signals distributed by the remote audio control unit may begenerated from a tracking power supply, and may be generally low voltagein nature, on the average, but with occasional transient excursionsabove the normal supply rail level when needed to drive peak sound inthe audio program. It is typically desirable to have the power supplyrail be two to three volts above the level of the audio signal waveformwhen tracking. For normal low output level conditions, the trackingpower supply may default to a certain minimum output voltage. Peaks inthe audio waveform, however, may run up against the normal supply raillevel and cause noise and potentially lead to power inefficiencies aswell. It would therefore be advantageous to raise the power supply railsas needed temporarily when the audio waveform reaches transient peaklevels. Where the amplifier output stage is integrated or collocatedwith the speaker unit, however, it is generally undesirable to have apower supply also integrated with the speaker unit, for safety reasonsand because of municipal codes. A tracking power supply in the audiocontrol unit which distributes low average voltage power signals (butwith occasional transient peaks) solves the foregoing problem byallowing the power supply to remain remotely located while providingboost power when needed by the speaker unit.

In certain embodiments, both power signals and audio signals aretransmitted from the remote audio control unit to the speaker unit(s).One possible tracking power supply that may be used in the remote audiocontrol unit is the type disclosed in U.S. Provisional Application Ser.No. 60/980,344 entitled “Efficient Power Amplifier,” assigned to theassignee of the present invention, and incorporated by reference as ifset forth fully herein. The power signals typically remain at the normalsupply rails, e.g., ±12-14 volts, and so they would generally be deemedlow voltage signals and hence present no more safety concern than audiosignals. A tracking power supply in the audio control unit maytemporarily boost the supply rails when the audio waveform approachesthe supply rails, but since such excursions are short the average poweris not significantly affected. The fluctuations in the distributed powersignals should not cause interference because they are generally lowfrequency in nature. Moreover, relatively narrow gauge wires can be usedto carry the power signals from the audio control unit to the speakerunits, since the power level on average remains low. Thus, according tocertain embodiments, an amplifier output stage may be integrated orcollocated with the speaker unit, in the context of a sound systemhaving improved noise immunity, low interference, increased powerefficiency, and no added safety risk.

FIG. 10 is a diagram illustrating an example of a sound system 1000having a remote audio control unit 1002 and multiple speaker units 1020,1030, 1040 generally configured as speaker line arrays, with theamplification stages for the speaker units split at different locations(i.e., part of the amplification occurs at the audio control unit 1002and part at each of the respective speaker units 1020, 1030 and 1040).The speaker units 1020, 1030, 1040 may be embodied, for example, as anyof the speaker units previously described herein—such as thoseillustrated in any of in FIG. 2A-2B, 3A-3B, 5, 7, 8, 19A-D, or 20A-F, orany other suitable speaker unit or line array. In the particular exampleof FIG. 10, the speaker units 1020, 1030, 1040 are arranged as a leftspeaker unit, center speaker unit, and right speaker unit, respectively;however, the principles described herein are applicable to various otherconfigurations of speaker units and any number thereof.

In FIG. 10, various audio input signals 1012, 1013, 1014 (such as left,center and right audio signals, respectively) may be provided to anaudio control unit 1002. These inputs may, but need not, be analog innature. The audio control unit 1002 may provide functions includingsystem interface, control, audio distribution and power distribution, orany subset thereof, as well as additional functions if desired. Theaudio control unit 1002 may also include a low frequency effects (LFE)input 1015, which may likewise be analog in nature, and a standard powerinput 1016. The audio control unit 1002 may provide, as outputs, digitalaudio signals 1024, 1034, 1044 and associated variable power signals1025, 1035, 1045 for the left, center and right speaker units 1020,1030, 1040, respectively. The variable power signals 1025, 1035, 1045may be generated by stepping down a standard wall voltage to a lowerlevel, such as ±12-14 Volts, and using a tracking power supply of thetype described, for example, in U.S. Provisional Application Ser. No.60/980,344, previously incorporated by reference as if set forth fullyherein. In such an embodiment, the power supply preferably is capable oftracking at a rate greater than the highest frequency of the audiosource signal that is being amplified. Alternatively, the audio unit1002 may include a bridge amp in conjunction with a modulated supplyvoltage that is lifted above the DC supply voltage when a larger outputvoltage swing is required. Other amplifier types may also be used,depending upon the application and the needs of the speaker unit. It mayalso be desirable in certain embodiments to include over-current and/orover-voltage protection circuitry in connection with the tracking powersupply signals.

The ability to temporarily raise the power supply voltage above thenominal supply level, as needed, can provide a number of advantages.Among other things, a higher voltage requires less current for the samewattage, and less current in turn means that the signal cables can bethinner. Use of a tracking power supply, as opposed to a class Damplifier for example in the output stage, may avoid the need for apassive LC output filter with its associated inductor that can be hardto implement and create electromagnetic interference problems.

For the left speaker unit 1020, the audio control unit 1002 in thisexample provides a digital audio signal 1024 to be conveyed to a digitalaudio processor 1022, and a variable power signal 1025 which is conveyedto an amplifier 1021. The amplifier 1021 also receives the output of thedigital audio processor 1022 and conveys a digitally processed andamplified audio output signal to the left speaker unit 1020. The centerand right speaker units 1030, 1040 are likewise configured with digitalaudio processors 1032, 1042 and amplifiers 1031, 1041, which outputprocessed and amplified audio signals to the center and right speakerunits 1030, 1040, respectively.

In a preferred embodiment, for a given speaker unit 1020, 1030 or 1040,the associated digital audio processor 1022, 1032 or 1042 and amplifier1021, 1031 or 1041 (referred to collectively for convenience as thespeaker unit receiving electronics) are collocated with the particularspeaker unit 1020, 1030 or 1040—that is, the speaker unit receivingelectronics may be housed within the same enclosure as the drive units,or otherwise attached to, embedded within, or positioned nearby oradjacent to the speaker units 1020, 1030, and 1040. Digital audiosignals 1024, 1034, 1044 and variable power signals 1024, 1035, 1045 arepreferably conveyed over a low power speaker cable such as, for example,an ISO Category 5 (“CAT5”) cable or a modified version thereof. Forexample, a CAT5 cable may be combined with a 4-conductor speaker wire toform a modified CAT5 cable that carries both the digital audio andcommunication signals (1024, 1034 or 1044) and the variable powersignals (1025, 1035 or 1045) for the amplifiers 1021, 1031, or 1041.Other cable types may also be used, including cables rated for lowvoltage/current, depending upon the nature of the speaker systemarchitecture.

FIGS. 11A and 11B are detailed circuit block diagrams of anotherembodiment of an audio system, having a remote audio control unit andseparate speaker unit receiving electronics collocated with one or morespeaker units, according to another example. FIG. 11A is a circuit blockdiagram of an audio control unit portion of the sound system, while FIG.11B is a circuit block diagram of a speaker/receiver portion of thesound system. As shown first in FIG. 11A, an audio control unit 1102receives audio input signals 1107 which may include left, center andright audio signals, and may (but need not be) analog in nature. Theaudio control unit 1102 may also receive a low frequency effects (LFE)audio input signal 1115. The audio input signals 1107 and 1115 may beprovided to digital equalizers 1112, 1113 for processing and effects,some of which are described later herein. Digital equalizer 1112 mayoutput processed digital signals 1108 which may include left, center andright audio signals, and may be in a format such as I2S (which is a wellknown stereo audio transmission standard). The processed digital signals1108 may be provided to a digital transmission hub 1120, which conveysaudio output signals 1134 to, e.g., left, center and right speaker unitssimilar to the speaker units (1020, 1030 and 1040) illustrated in FIG.10. The audio output signals 1134 may include left, center and rightaudio data, and may be converted to a format such as CAT5, or othersignal format as may be used in the system.

The other digital equalizer 1113 may output a subwoofer (SW) analogoutput signal 1132, and may also provide interfaces to an LCD andswitches 1137, or a host computer (PC) interface 1137. The digitalequalizers 1112, 1113 may communicate internally with the digitaltransmission hub 1120, LCD and switches 1137, and host computerinterface 1137 via, e.g., a two-way communication protocol such as thestandard RS485 protocol, as indicated by communication and controlsignals 1106, 1109. An incoming power signal 1116 may be provided to apower input module 1140 which may include, e.g., a power switch,fuse(s), surge arrestor, and/or auto-resetting overload protection (PCT)circuitry. The power input module 1140 may be coupled to a firsttransformer 1148 which provides 12-14 volt unregulated DC power to othercomponents in the audio control unit 1102, in conjunction withrectifiers and/or smoothing capacitors 1149 if necessary. The powerinput module 1140 may also be coupled to a second transformer 1141 whichprovides a speaker power output signal 1145 that may be conveyed, e.g.,to the various speaker units 1020, 1030, 1040. In this example, thespeaker power output signal 1145 may have a swing of approximately ±33volts DC, and may physically comprise multiple (e.g., four)conductors/wires.

Turning now to FIG. 11B, a receiver electronics unit 1150 may beassociated with each speaker unit 1190, in a general systemconfiguration similar that illustrated in FIG. 10 with left, center andright speaker units 1020, 1030, 1040. In other words, while thecomponents for only a single speaker unit 1190 are shown in FIG. 11B,additional speaker units can be similarly constructed in the context ofa larger audio system. The receiver electronics unit 1150 in the exampleof FIG. 11B may include a digital receiver hub 1150 for receiving anddistributing the audio output signals 1034 from the audio control unit1102 (FIG. 11A). The digital receiver hub 1151 may output digitalaudio/control signals 1155 to an array of digital equalizers 1160, eachof which may have a plurality of channels (e.g., six channels). Digitalaudio/control signals 1155 may include one or more unidirectionaloptical pulse coded modulation (PCM) signal(s) and one or more two-waycommunication/control signal(s) carried over, e.g., an RJ12 connector orany other suitable connector.

The digital equalizers 1160 interpret any control information conveyedby digital audio/control signals 1155 and apply appropriatepre-processing—for example, to create some of the steering, shading,delay or other effects described herein. The digital equalizers 1160 mayalso convert the encoded digital audio data to analog form, and provideprocessed analog audio signals 1168 to one or more low frequencyamplifiers 1165 and one or more high frequency amplifiers 1166. The lowfrequency amplifiers 1165 drive the individual low/mid frequency driveunits of the speaker unit 1190, while the high frequency amplifiers 1166may drive the high frequency drive units of the speaker unit 1190. Thedigital equalizers 1160 may provide delay signals to simulate a curvedline array shape and/or for Legendre shading, as previously describedherein. Alternatively, as likewise previously described, passive meansmay be used for this purpose, thereby reducing the number of amplifiersrequired. For example, each drive unit's sensitivity may be individuallydesigned to match that required for a particular position in the array(aided in part by either series or parallel connection of the driveunits in an opposing pair configuration). Alternatively, or in addition,a passive attenuating network may be placed in series with the amplifierand a given drive unit. Similarly, a passive delay network may also beused in series with an amplifier and a particular drive unit, tailoredto the delay required for a particular location in the speaker linearray for simulating a curved line array.

The receiver electronics unit 1150 may further include power electronicsfor receiving and distributing the power output signal 1145 from theaudio control unit 1102. In a particular preferred embodiment, thereceiver electronics unit 1150 may drive up to 32 channels; however,smaller or larger arrays may be created as necessary for variousapplications. The power electronics may include an amplification module1170 (which may comprise a power amplifier and protection circuitry) andmay further include a voltage regulator 1171. The voltage regulator 1171may provide regulated or unregulated low voltage (e.g., 12-volt) DCpower to the digital equalizers 1160. The amplification module 1170 maydistribute the incoming power to the various amplifiers 1165, 1166. Theamplification module 1170 may comprise, for example, a variable ormodulated supply voltage that tracks the audio input signal andtemporarily boosts the positive and/or negative supply rails for peakaudio swings, such as may be provided by any of the tracking powersupplies described in U.S. Provisional Application Ser. No. 60/980,344,previously incorporated by reference.

In alternative embodiments, the amplification module 1170 may be movedupstream to the transmitter/power supply components of the audio controlunit 1102 of FIG. 11A and combined therewith. In such a case, the audiocontrol unit 1102 may be configured to output one or more relatively lowvoltage variable power supply signals (using a tracking power supply asdescribed above) for distribution to the various receiving electronicsof the speaker units (FIG. 11B), similar to the technique(s) describedearlier with respect to FIG. 10. In such a case, it may be possible tocombine the variable power supply signals with the signals beingtransmitted over the CAT5 or other cables to the speaker units.

The electronics for the audio control unit 1002 (FIG. 10) or 1102 (FIG.11A) may be provided, for example, in a standalone audio componenthousing similar to a conventional DVD or CD player, receiver, or thelike. FIG. 12 is a high level diagram illustrating an audio control unit1210 along with other possible components of a sound system 1200, shownfor purposes of illustration only and not limitation. In this example, aDVD player 1225 and preamplifier 1220 are provided in the sound system1200. The audio control unit 1200 is shown connected to left, right andcenter speaker units 1220, 1230, 1240 via a combination of CAT5 cable(s)1234 and 4-conductor speaker wire 1225, 1235, 1245 serving the left,center, and right speaker units 1220, 1230, 1240, respectively. Althoughconceptually shown as separate cables, the CAT5 cable(s) 1234 and4-conductor speaker wire 1225, 1235, 1245 may be combined individuallyfor each of the three speaker units 1220, 1230, and 1240, or otheralternative cables or wires may be utilized if desired.

In some cases it may be desirable to provide a composite speaker unitthat can be constructed of individual modular components. For example,one or more basic modular sub-arrays of drive units, each beingsubstantially identical in configuration, can be physically connectedtogether to form a larger speaker line array. In this manner, differentsizes of speaker line arrays can be created from the same basecomponents. If desired, each of the modular sub-arrays can beconstructed with its own amplifier output stage and audio processingelectronics, so that each sub-array is independent although there may bean audio control unit that sends each sub-array the appropriate audioinformation or instructions for proper sound reproduction in accordancewith the principles already described herein. As one example, a modularsub-array may be approximately 765 mm in length, with 70 mm lowfrequency drive units placed 90 mm apart (center to center). In thisexample, a total of eight low frequency drive units are placed on eachof the left and right arrays, for a total of 720 mm for each array, butwhere the left and right arrays are staggered the total length of themodular sub-array is around 765 mm. Because of the staggering of theleft and right arrays, the modular units may be constructed with aremovable cap on each end (e.g., a top cap on the left array side and abottom cap on the right array side); when placing two sub-arraystogether, the top cap would be removed from the lower sub-array and thebottom cap from the upper sub-array. In this manner, no interruptionoccurs in the staggered line array pattern. Any number of sub-arrays maybe combined in this fashion to form a larger speaker unit.

In an alternative embodiment, two speaker linear arrays may be combinedwith one line array vertically oriented and the other horizontallyoriented, in, for example, an “X” pattern in which the two arraysoverlap in the middle. The individual line arrays may be controlled inaccordance with techniques described herein, to provide atwo-dimensional array with controllable directivity based on twoone-dimensional line arrays.

Various effects as may be created with speaker units or line arraysconstructed in accordance with certain embodiments disclosed herein willnow be further described. In a particularly versatile configuration of aspeaker unit or line array, all the drive units in the line array areseparately addressable by multi-channel DSP, and preferably integratedwith power amplifiers, that can thereby provide effects such as controlof audio beamwidth and/or steering, as further explained below, and/orcreation of multiple audio beam overlays of distributed “equivalentspeakers” (or virtual speakers) from a single speaker unit or linearray. Examples of the foregoing effects may be explained with referenceto FIGS. 14A through 18. In the context of those figures, the term“speaker line array” will be used to refer to speaker unitconfigurations such as generally depicted in any of FIGS. 2A-2B, 3A-3B,5 and 8, as well as other variations including potentially a singlelinear speaker array using DSP processing according to techniquesexplained herein to steer or otherwise control the audio output in themanner described.

FIGS. 14A and 14B, for example, are conceptual diagrams illustrating thetailoring of audio beam width using a speaker unit in the form of aspeaker line array. In the example of FIGS. 14A and 14B, a speaker linearray 1410 is provided in a listening area 1400 (such as a media room,home theater, cinema, recording studio, etc.) with the expected audienceseating 1415 as shown. The speaker line array 1410 is illustrated inthis example as a flat speaker unit that is positioned horizontally. Ifhaving a slotted output as described previously in connection withvarious embodiments, the speaker line array 1410 may advantageously beembedded within a wall or mounted thereto; alternatively the speakerline array 1410 may be placed on a stand or otherwise conventionallymounted. Through digital processing using, e.g., DSPs, the width of theaudio beam projected by the speaker line array 1410 may be adjusted, andmay, for example, be controlled to be a wide beam 1420 (as in FIG. 14A)or a narrow beam 1421 (as in FIG. 14B). Control of the beam width isbased on selection of the appropriate Legendre parameters, as is knownin the art. The selection of beam width may be instigated by manualselection of a control option available via an audio unit (such as anamplifier/receiver or surround sound audio unit). Alternatively, thebeam width may be modified dynamically, or in real-time, in response tocontrol information in the audio source material or based upon anevaluation of the audio source material.

The audio beam width can be tailored to suit different acousticconditions. For example, narrow beams may be useful with live speakersor where there is substantial dialog, so as to improve voiceintelligibility. On the other hand, wide beams provide more completecoverage and enhance the perception of spaciousness. The control of theaudio beam characteristics, including beam width, can be real-time orelse pre-programmed with the source audio data.

Besides having control of the audio beam width, the speaker line arraymay also provide steerability of the audio beam. FIGS. 15A through 15Dare diagrams illustrating examples of steering of an audio beam using aspeaker line array 1510. FIG. 15A shows the situation where the audiobeam 1520 is directed down the center of the listening area 1500 towardsthe expected audience seating 1515. FIG. 15B shows the situation wherethe audio beam 1521 is directed to one side of the expected audienceseating 1515. FIGS. 15C and 15D illustrate situations where the audiobeams 1522, 1523 are directed to the far left and right sides,respectively of the expected audience seating 1515. To steer an audiobeam, the audio processor (such as 1022, 1032, 1042 in FIG. 10, or theelectronics of FIG. 11B) adjusts the timing of signals to various driveunits. More specifically, the audio processor adjusts the delay amountto each drive unit, effectively moving some drive units further back andsome drive units closer to the target area—conceptually similar to thesimulation of a curved surface through use of graduated delays asdescribed previously with respect to FIG. 22. The amount of delayadjustment for each drive unit may be readily calculated based upon thedesired steering angle, given the overall length of the line array (orsub-array) being steered and the relative position of each drive unit inthe line array. Generally, the center drive unit in the array orsub-array being steered will have a delay adjustment of zero (as it actsas the “pivot” point), while the amount of delay adjustment should besymmetrical around the center drive unit, with positive delay amounts onone side of the center drive unit and negative delay amounts on theother side.

Audio beam steering may be used to direct the sound of any channel ofthe speaker line array either toward or away from any listeningposition. Narrow audio beams useful for intelligibility in live roomscan be directed toward a listener sitting away from the main or centralaxis of the speaker line array 1510. Audio beams can be directed sharplyaway from the listeners to, for example, decrease direct/reflected soundratio and/or to improve the sense of ambience.

Since the speaker line array has a large number of channels, more thanone audio beam may be generated and controlled or steered from a singlespeaker line array, as illustrated in FIGS. 16A-16D, and the audio beamsmay be non-overlapping, partially overlapping, or fully overlapping, andmay have the same or different program content. For example, FIG. 16Aillustrates a situation where two audio beams (represented collectivelyby 1620), such as two audio vocal tracks, output from a speaker linearray 1610 are fully overlapping; whereas FIG. 16B illustrates thesituation where the two audio beams 1621, 1622 are steered to differentsides of the expected audience seating 1615 in the listening area 1600.FIGS. 16C and 16D represent the analogous situations as FIGS. 16A and16B, respectively, except with respect to a vocal track 1626 and musictrack 1627 instead of two vocal tracks. Although the examples areillustrated with two audio beams, the same concept can be expanded to anarbitrary number of audio beams.

The ability to generate and separately steer multiple audio beams mayprovide a number of advantages and benefits. For example, dialogue andmusic or special effects are often directed to the center channel,making dialogue difficult to hear unless volume is raised whichincreases total loudness; however, by steering the two components indifferent directions the ear/brain can readily separate them and listento either at will, without the need to raise the overall loudness.

The ability to separately address all the drivers in a line providesanother opportunity for an improved listening experience especially withregard to stable imaging. The most common way to provide more stable andbelievable imaging, particularly in front of the listener, is to havemore speakers. The ability of the inventive speaker line array toreproduce many different overlaid beams can be used to simulate theeffect of having multiple spatially separate speakers—which may betermed “real phantom images”—created from sub-arrays of drive unitswithin a single horizontal speaker line array. These equivalent orsimulated speakers not only may occupy separate physical positionsacross the sound stage, but also can each possess different directionalcharacteristics and be fed from separate sound channels. FIG. 17 is aconceptual diagram illustrating generation of real phantom images fromequivalent or simulated speakers using a speaker line array 1710. Asshown in the example of FIG. 17, five different groups 1731-1735 (someoverlapping) of contiguous drive units within the speaker line array1710 are combined in to create five real phantom images 1714. The DSPprocessing associated with the speaker line array 1710 is configured totreat each group 1731-1735 of drive units as a cohesive unit, andthereby provides the effect of having five spatially separate speakerunits and a broader, more stable sound stage.

According to certain aspects of the above described embodiment, it isgenerally possible to create an increased number of spatially separatereal phantom images at any position within the width of the speakerarray line. This effect is achieved by creating sub-arrays from thedrive units within a single, long horizontal array 1710. The number ofphantom images is limited in practice to about 90% of the drive unitsthe horizontal speaker line array 1710. Also, in practice, due to thelimited angular resolution of the ear it is unlikely that any increasein the number of real phantom images is needed for adjacent pairs tosubtend an angle of, e.g., less than 2-3 degrees at the listener.

Similarly, the use of the speaker line array 1710 may increase thenumber of apparent channels in the system. Currently the maximum numberof front and surround channels in a standard format is limited to seven,but through the process of up-mixing it is conceptually possible toundertake a spatial re-sampling process that increases the number ofchannels from seven up to a maximum approaching that of the total numberof drive units in the speaker line array 1710. In practice this isunlikely to be needed, but an increase from seven to, e.g., twenty orthirty would be readily achievable and the benefit immediately apparentin terms of image position and stability. These additional channels ofinformation needed to drive the sub-arrays could be provided in a numberof ways. For example, the additional channels of information could beobtained by spatial up-sampling of existing 5.1-7.1 program or sourcedata. This process could be carried out by providing directional andambient cues for each channel. During the original mixing process, suchinformation may be contained in metadata accompanying the audio program.After the original mixing process, the ambient and directional cues maybe separated from an existing 5.1-7.1 program down-mix. A spatialup-sampling technique has already been developed for up-mixing fromstereo to 5.1 and could be adapted for up-mixing from 5.1. For each ofthe up-sampled channels the estimated spatial position and ambientcontent could be used to create a separate overlay assigned to asub-array in the horizontal speaker line array 1710. Besides spatialup-sampling of existing 5.1-7.1 program data, the additional channels ofinformation might be obtained in certain circumstances from an originalmulti-channel master stored with sufficient channels to provide aseparate audio channel for every drive unit or sub-array.

A full playback system in a home theater environment, for example, mightconsist of four long speaker line arrays mounted horizontally on (orwithin) each wall—front, back and either side. FIG. 18 is a diagramillustrating an example of such a configuration, with speaker linearrays 1820, 1830, 1840 and 1850 surrounding the expected audienceseating 1815 on all sides. Such an arrangement should be capable ofproducing a near 3-D horizontal image that is both stable and accurateover a wide listening area. The sound system, and each speaker linearray 1820, 1830, 1840, 1850 therein, may be programmed or tuned atsetup time to take advantage of the particular nature of the room 1800.

A speaker line array according to various aforementioned embodiments mayprovide advantages such as improved intelligibility under liveconditions by varying beam width; improved intelligibility under liveconditions by overlaying separately steered beams; creating a largersweet spot by steering or beam widening, and reducing timbral colorationby reducing unwanted reflection. In one aspect, controllable directivityis utilized by the speaker line array to minimize the effects ofspeaker/room interaction.

Speaker units or line arrays constructed according to certainembodiments and variations disclosed herein may find a wide range ofcommercial, consumer, and practical applications. As one example,speaker units or line arrays as described herein may be advantageouslyutilized for providing cinematic sound systems as used in, e.g., movietheaters and the like. Front speaker line arrays can provide widecoverage for substantially all of the seats in a theater, in addition toproviding improved dialog intelligibility and sound quality even atrelatively low playback levels. Speaker line arrays arranged in asurround configuration may provide more realistic ambient effects aswell as rear directional cues simultaneously from the same physicalarray. Also, separate beams can be used for dialog and effects; thisallows, for example, the audio effects volume to be suppressed slightly(if desired) in the center channel, where the dialog audio is output,while keeping the effects at normal volume in the right and leftchannels where it is less likely to interfere with dialog. For largespeaker line arrays positioned on the sides of a theater, fore and afteffects could also be realized, if desired by the sound designer ormixer.

Another application for speaker line arrays is in home theater soundsystems. For example, speaker line arrays—particularly those using soundoutput slots—may allow a slim forward speaker profile, enabling lessconspicuous speakers to be installed on or in the wall, and may act asdirect replacement for existing 5.1 surround systems. Many more seatingpositions can be used in the home theater area without compromisingsound timbre or imaging. Shaped and directed beams can minimizeundesired room effects. The system can adjusted or programmably tuned tosuit the customer's requirements with regard to speaker placement andlistening position. Most audio formats could be correctly replayed over,e.g., a four-line horizontal array without the need to change thespeaker layout for different audio formats. For example, most or all ofsurround formats 5.0, 5.1, 6.0, 6.1, 7.0 and 7.1 could be correctlyreplayed on the same four-line horizontal array, without the need to addmore speakers or alter the positioning of speakers.

Another application for speaker line arrays is for game sound systems.For example, a horizontal four line array layout may be ideally suitedfor the realistic creation of all-round sound effects that track theon-screen action (whether on a television screen, flatscreen, or acomputer screen).

Yet another application for speaker line arrays is in recording studios.For example, steerable speaker line arrays may be used to provideseparate but equivalent beams to both the audio engineer responsible formixing, and the customer who is normally seated at a different locationin the recording studio. As with the home theater system, a singlespeaker layout (with four horizontal line arrays) can be used to emulatemany other speaker configurations by software control. Differentsurround formats with varying numbers of replay channels or speakers canalso be simulated with the line array speaker arrangement.

Yet another application for speaker line arrays is for soundreinforcement. The ability to control beam direction and width using thespeaker line array and associated processing may be especially usefulfor sound reinforcement where intelligibility and coverage are neededunder a variety of acoustic conditions. Such a technique may be usedeither indoors or outdoors.

In one aspect, according to certain embodiments as disclosed herein, aspeaker unit is provided having a slim profile with integrated DSP andindividual power amplifiers for each drive unit. In another separateaspect, a speaker unit is provided having audio beams which aresteerable and/or expandable (or contractable) through software control,in real time or as pre-programmed in the source audio data, andproviding the ability to partially or fully overlay multiple beams ofdifferent widths and having different audio content.

Various embodiments of slotted speaker units as described herein mayprovide a number of advantages, depending potentially upon the specificconfiguration, environment, and other factors. For example, a slottedspeaker unit may have the effect of transforming an elliptical soundradiator (i.e., conventional conical speaker) and effectively transformit into, e.g., a rectangular or almost linear sound radiator, withexcellent coverage at the radiated angles. In addition to sound quality,a slotted speaker unit may provide opportunity to improve the packagingand appearance of the speaker unit. Use of an output slot to radiatesound provides the opportunity for placing drive units closer to eachother, reducing out-of-phase, cross-cancellation, and lobing effectsthat may otherwise occur from the use of multiple speakers.

In any of the foregoing embodiments, the audio source from which thevarious audio input signals are derived, before distribution to thespeaker unit(s) or other system components as described herein, maycomprise any audio work of any nature, such as, for example, a musicalpiece, a soundtrack to an audio-visual work (such as a DVD or otherdigitally recorded medium), or any other source or content having anaudio component. The audio source may be read from a recorded medium,such as, e.g., a cassette, compact disc, CD-ROM, or DVD, or else may bereceived wirelessly, in any available format, from a broadcast orpoint-to-point transmission. The audio source may be in an encodedformat, such as a surround sound or other multi-channel format,including Dolby-AC3, DTS, DVD-Audio, etc. The audio source may alsocomprise digital files stored, temporarily or permanently, in any formatused for audio playback, such as, for example, an MP3 format or adigital multi-media format.

Unless otherwise specified, the various embodiments described herein canbe implemented using either digital or analog techniques, or anycombination thereof. The term “circuit” as used herein is meant broadlyto encompass analog components, discrete digital components,microprocessor-based or digital signal processing (DSP), or anycombination thereof. The invention is not to be limited by theparticular manner in which the operations of the various soundprocessing embodiments are carried out.

While examples have been provided herein of certain preferred orexemplary sound processing characteristics, it will be understood thatthe particular characteristics of any of the system components may varydepending on the particular implementation, speaker type, relativespeaker spacing, environmental conditions, and other such factors.Therefore, any specific characteristics provided herein are meant to beillustrative and not limiting. Moreover, certain components may beprogrammable so as to allow tailoring to suit individual sound taste.

While certain system components are described as being “connected” toone another, it should be understood that such language encompasses anytype of communication or transference of data, whether or not thecomponents are actually physically connected to one another, or elsewhether intervening elements are present. It will be understood thatvarious additional circuit or system components may be added withoutdeparting from teachings provided herein.

In some of the embodiments described herein, the speakers utilized inthe sound system may be passive or active in nature (i.e., with built-inor on-board amplification capability). In most or all of theembodiments, the various audio channels may be individually amplified,level-shifted, boosted, or otherwise conditioned appropriately for eachindividual drive unit or speaker unit.

While preferred embodiments of the invention have been described herein,many variations are possible which remain within the concept and scopeof the invention. Such variations would become clear to one of ordinaryskill in the art after inspection of the specification and the drawings.The invention therefore is not to be restricted except within the spiritand scope of any appended claims.

1. A sound reproduction system, comprising: a first speaker line arrayand a second speaker line array, each speaker line array comprising aplurality of drive units arranged such that the drive units of the firstspeaker line array face an opposing direction from the drive units ofthe second speaker line array; a sound reflecting surface disposed infront of each drive unit, whereby acoustic output radiated from thedrive unit is compressed and turned; and one or more sound output slotsfor emanating sound from the drive units; wherein the drive units ineach of the speaker line arrays provide audio output in accordance witha Legendre shading function.
 2. The sound reproduction system of claim1, wherein the sound reflecting surface is disposed substantiallyparallel with a longitudinal axis of both of the first and secondspeaker line arrays, and wherein the sound output from the drive unitsis turned by the sound reflecting surface so that it is redirectedapproximately perpendicularly from its initial direction.
 3. The soundreproduction system of claim 2, wherein the forward acoustic radiationfrom each of the drive units is acoustically isolated from its rearwardacoustic radiation.
 4. The sound reproduction system of claim 1, whereinthe drive units of each of the speaker line arrays are physicallyarranged in an arc pattern in accordance with the Legendre shadingfunction.
 5. The sound reproduction system of claim 1, wherein the driveunits of each of the speaker line arrays are aligned along anapproximately straight axis.
 6. The sound reproduction system of claim5, further comprising delay circuitry whereby an input signal isselectively delayed for each of said drive units or groups thereof so asto simulate the effect of the drive units being arranged in an arcpattern.
 7. The sound reproduction system of claim 1, further comprisinga sound processor whereby each of said drive units receive a processedinput signal having Legendre shading corresponding to a location of thedrive unit in each speaker line array.
 8. The sound reproduction systemof claim 1, wherein the drive units in the first speaker line array arepositioned directly opposite and facing the drive units in the secondspeaker line array.
 9. The sound reproduction system of claim 1, whereinthe drive units in the first speaker line array are facing and evenlystaggered with respect to the drive units in the second speaker linearray.
 10. A sound reproduction system, comprising: a speaker line arraycomprising a first plurality of drive units aligned along anapproximately straight axis and disposed towards a sound reflectingsurface, such that sound output from the drive units is compressed andturned towards an elongate output slot; a second plurality of driveunits arranged so that their sound output is directed in substantiallythe same direction as the sound from the first plurality of drive unitsemanating from the elongate output slot, said second plurality of driveunits having higher frequency response than said first plurality ofdrive units; and a sound processor outputting a plurality of audiooutput signals, whereby each drive unit in the speaker line arrayreceives an audio output signal having Legendre shading corresponding tothe respective position of the drive unit in the speaker line array. 11.The sound reproduction system of claim 10, wherein the sound reflectingsurface is disposed substantially parallel with a longitudinal axis ofthe speaker line array, and wherein the sound emanating from the driveunits is turned by the sound reflecting surface so that it is redirectedapproximately perpendicularly from its initial direction.
 12. The soundreproduction system of claim 11, wherein the forward acoustic radiationfrom each of the drive units is acoustically isolated from its rearwardacoustic radiation.
 13. The sound reproduction system of claim 10,further comprising delay circuitry whereby an audio input signal isselectively delayed for each drive unit of the speaker line arraydepending upon its respective position in the speaker line array, so asto simulate the effect of the drive units being arranged in an arcpattern.
 14. The sound reproduction system of claim 10, furthercomprising a second speaker line array comprising a third plurality ofdrive units aligned along an approximately straight axis and disposedtowards a second sound reflecting surface, such that sound output fromthe drive units of the second speaker line array is compressed andturned towards a second elongate output slot substantially parallel withsaid first elongate output slot.
 15. The sound reproduction system ofclaim 14, wherein the drive units in the second speaker line array arepositioned directly opposite and facing the drive units in the firstspeaker line array.
 16. The sound reproduction system of claim 14,wherein the drive units in the second speaker line array are facing butstaggered with respect to the drive units in the first speaker linearray.
 17. The sound reproduction system of claim 14, wherein the secondplurality of drive units are arranged along the same longitudinal axisas the first and second elongate output slots.
 18. The soundreproduction system of claim 17, wherein the second plurality of driveunits are positioned in front of the first and second elongate outputslots, such that the second plurality of drive units are in thesoundpath of sound emanating from either or both of the first and secondspeaker line arrays.
 19. A sound reproduction system, comprising: afirst plurality of drive units arranged in a row, perpendicular to aspeaker unit front; a second plurality of drive units arranged in a row,perpendicular to the speaker front, positioned such that the secondplurality of drive units are facing towards the first plurality of driveunits and are staggered with respect thereto; a plurality of sound ductsfor conveying acoustic output from said first plurality of drive unitsand said second plurality of drive units in a direction perpendicular tothe orientation of the drive units; and one or more elongate aperturesdisposed at a terminating end each of the sound ducts for allowingforward acoustic radiation from the drive units to be radiated from thespeaker unit front.
 20. The sound reproduction system of claim 19,further comprising a sound processor collocated with the speaker unitfor providing audio signals to the drive units.
 21. The soundreproduction system of claim 20, wherein said sound processor providesto each of said drive units a processed input signal having Legendreshading corresponding to a location of the drive unit in its respectiverow of drive units.
 22. The sound reproduction system of claim 21,wherein said sound processor comprises a digital signal processor whichreceives said input signal, calculates a delay value for each drive unitbased upon a Legendre shading function, and applies the calculated delayvalue to the audio output signal provided to each drive unit.
 23. Thesound reproduction system of claim 19, wherein said first plurality ofdrive units are evenly staggered with respect to the second plurality ofdrive units, such that each drive unit of the first plurality of driveunits not at an end of the first row is approximately centered relativeto the two nearest opposing drive units in the second row, and viceversa.
 24. The sound reproduction system of claim 19, wherein theforward acoustic radiation from each of the drive units is acousticallyisolated from its rearward acoustic radiation.